16.1.07
Animated Chemistry
Subjects are in Alphabetical Order
Acid (Strong vs. Weak Acid)
Activation Energy
Atomic and Molecular Orbitals
Atomic Radius
Buffers (Acetate Buffer)
Emission Spectra
Galvanic Cell
Hybridization
Hydrogen Bonding
Ideal Gases
LeChatelier's Principle
Limiting Reagents
Reactions (Collisions in Reactions)
Vapor Pressure
Acid (Strong vs. Weak Acid)
Activation Energy
Atomic and Molecular Orbitals
Atomic Radius
Buffers (Acetate Buffer)
Emission Spectra
Galvanic Cell
Hybridization
Hydrogen Bonding
Ideal Gases
LeChatelier's Principle
Limiting Reagents
Reactions (Collisions in Reactions)
Vapor Pressure
15.1.07
Atomic Structure
[HOME] [HEURISTICS] [NUMBERS AND MATH] [UNITS AND MEASURES] [ATOMIC STRUCTURE] [ELEMENTS] [PERIODIC TABLE] [STATES OF MATTER] [COMPOUNDS] [REACTIONS] [MOLS, PERCENTS, AND STOICHIOMETRY] [REDOX AND ELECTROPLATING] [GASES] [SOLUTIONS] [ACIDS AND BASES] [KINETICS] [THERMOCHEMISTRY]
ATOMIC STRUCTURE
And you thought you were strangeAtomic weights and atomic numbers.Formula weight or molecular weight.Electron configuration.Electron configuration chart.Common electron configuration scheme.Octet rule as seen on the periodic chart.Sideways periodic chart with electron shell numbers.Lewis structures of elements.
AND YOU THOUGHT YOU WERE STRANGE
Here is an outrageous thought: All the matter around you is made of atoms, and all atoms are made of only three types of subatomic particle, protons, electrons, and neutrons. Furthermore, all protons are exactly the same, all neutrons are exactly the same, and all electrons are exactly the same. Protons and neutrons have almost exactly the same mass. Electrons have a mass that is about 1/1835 the mass of a proton. Electrons have a unit negative charge. Protons each have a positive charge. These charges are genuine electrical charges. Neutrons do not have any charge.
Even more outrageous is the shape of the atoms with the three subatomic particles. The neutrons and protons are in the center of the atom in a nucleus. The electrons are outside the nucleus in electron shells that are in different shapes at different distances from the nucleus. The atom is mostly empty space. Ernest Rutherford shot subatomic particles at a very thin piece of gold. Most of the particles went straight through the gold. It was like shooting a rifle into a thin line of trees. Some of the particles bounced off, some stuck inside, but the major portion of them passed through the gold foil. By Rutherford?s calculations, the nucleus in an atom is like a B-B in a boxcar. That is a genuinely outrageous idea. Almost all the mass of an atom is concentrated in the tiny nucleus. The mass of a proton or neutron is 1.66 E -24 grams or one AMU, atomic mass unit. The mass of an electron is 9.05 E -28 grams. This number is a billionth of a billionth of a billionth of a gram. It is not possible for anyone or any machine that uses light to actually see a proton using visible light. The wavelength of light is too large to be able to detect anything that small.
Back to the beginning of Atomic Structure.
ATOMIC WEIGHTS AND ATOMIC NUMBERS
The integer that you find in each box of the Periodic Chart is the atomic number. The atomic number is the number of protons in the nucleus of each atom. Another number that you can often find in the box with the symbol of the element is not an integer. It is oversimplifying only a little to say that this number is the number of protons plus the average number of neutrons in that element. The number is called the atomic weight or atomic mass.
How can it be that an element must have an averaged atomic weight? The number of protons defines the type of element. If an atom has six protons, it is carbon. If it has 92 protons, it is uranium. The number of neutrons in the nucleus of an element can be different, though. Carbon 12 is the commonest type of carbon. Carbon 12 has six protons (naturally, otherwise it wouldn?t be carbon) and six neutrons. The mass of the electrons is negligible. Carbon 12 has a mass of twelve. Carbon 13 has six protons and seven neutrons. Carbon 14 has six protons and eight neutrons. Carbon 14 is radioactive because, as other atoms with the wrong percentage of neutrons to protons, it is unstable. The nucleus tends to pop apart. The proper ratio of protons to neutrons is about one to one for small elements and about one proton to one and a half neutrons for the larger elements. Types of an element in which every atom has the same number of protons and the same number of neutrons are called isotopes. Carbon 14 is a radioactive isotope of carbon. Any carbon 14 that was made at the time the earth was formed is now almost all gone. Carbon 14 is continuously made from high energy electromagnetic radiation hitting nitrogen atoms in the ozone layer of the earth. This carbon 14 when taken into plants as CO2 will also be taken into animals. We can find out how much carbon 14 that normally is in a living plant or animal and from there we can find the actual amount of carbon 14 left in a plant or animal long dead. We can get a very good idea of how long ago that plant or animal was living from the amount of carbon 14 remaining in the dead body. This process is called ?carbon dating.? The stable, non-radioactive isotopes of carbon play no part in this. As a whole element, carbon has a more or less fixed proportion of the various carbon isotopes. For this reason, we can determine a weighted average of the isotopes for all elements. On a periodic chart you may see some atomic weights that are integers or in parentheses. These are usually on the very large or very rare or very radioactive elements. That is not really an integer atomic weight, but the atomic weight has been estimated to the nearest integer.
Back to the beginning of Atomic Structure.
FORMULA WEIGHT OR MOLECULAR WEIGHT OR FORMULA MASS OR MOLAR MASS
Now with the atomic weight information we can consider matching up atoms on a mass-to-mass basis. Let?s take hydrogen chloride, HCl. One hydrogen atom is attached to one chlorine atom, but they have different masses. A hydrogen atom has a mass of 1.008 AMU and a chlorine atom has a mass of 35.453 AMU. Practically speaking, one AMU is far too small a mass for us to weigh in the lab. We could weigh 1.008 grams of hydrogen and 35.453 grams of chlorine, and they would match up exactly right. There would be the same number of hydrogen atoms as chlorine atoms. They could join together to make HCl with no hydrogen or chlorine left over. If we take one gram of a material for every AMU of mass in the atoms of just one of them, we will have a mol (or mole) of that material. One mol of any material, therefore, has the same number of particles of the material named, this number being Avogadro?s number, 6.022 E 23.
The formula weight is the most general term that includes atomic weight and molecular weight. In the case of the HCl, we can add the atomic weights of the elements in the compound and get a molecular weight. The molecular weight of HCl is 36.461 g/mol, the sum of the atomic weights of hydrogen and chlorine. The unit of molecular weight is grams per mol. The way to calculate the molecular weight of any formula is to add up the atomic weights of all the atoms in the formula. CuSO4?5H2O is copper II sulfate pentahydrate. The formula has one copper atom, one sulfur atom, nine oxygen atoms, and ten hydrogen atoms. To get the formula weight of this compound we would add up the atomic weights. Copper II sulfate pentahydrate is not a molecule, strictly speaking, but you will hear the term ?molecular weight? used for it rather than the more proper ?formula weight.' Since the unit of formula weight is grams per mol, it makes good sense to use the formula weight of a material as a conversion factor between the mass of a material and the number of mols of the material.
Back to the beginning of Atomic Structure.
ELECTRON CONFIGURATION
Protons have a positive charge and electrons have a negative charge. Free (unattached) uncharged atoms have the same number of electrons as protons to be electrically neutral. The protons are in the nucleus and do not change or vary except in some nuclear reactions. The electrons are in discrete pathways or shells around the nucleus. There is a ranking or heirarchy of the shells, usually with the shells further from the nucleus having a higher energy. As we consider the electron configuration of atoms, we will be describing the ground state position of the electrons. When electrons have higher energy, they may move up away from the nucleus into higher energy shells. As we consider the electron configuration, we will be describing the ground state positions of the electrons.
A hydrogen atom has only one proton and one electron. The electron of a hydrogen atom travels around the proton nucleus in a shell of a spherical shape. The two electrons of helium, element number two, are in the same spherical shape around the nucleus. The first shell only has one subshell, and that subshell has only one orbital, or pathway for electrons. Each orbital has a place for two electrons. The spherical shape of the lone orbital in the first energy level has given it the name ?s? orbital. Helium is the last element in the first period. Being an inert element, it indicates that that shell is full. Shell number one has only one s subshell and all s subshells have only one orbital. Each orbital only has room for two electrons. So the first shell, called the K shell, has only two electrons.
Beginning with lithium, the electrons do not have room in the first shell or energy level. Lithium has two electrons in the first shell and one electron in the next shell. The first shell fills first and the others more or less in order as the element size increases up the Periodic Chart, but the sequence is not immediately obvious. The second energy level has room for eight electrons. The second energy level has not only an s orbital, but also a p subshell with three orbitals. The p subshell can contain six electrons. The p subshell has a shape of three dumbbells at ninety degrees to each other, each dumbbell shape being one orbital. With the s and p subshells the second shell, the L shell, can hold a total of eight electrons. You can see this on the periodic chart. Lithium has one electron in the outside shell, the L shell. Beryllium has two electrons in the outside shell. The s subshell fills first, so all other electrons adding to this shell go into the p subshell. Boron has three outside electrons, carbon has four, nitrogen has five, oxygen has six, and fluorine has seven. Neon has a full shell of eight electrons in the outside shell, the L shell, meaning the neon is an inert element, the end of the period.
Beginning again at sodium with one electron in the outside shell, the M shell fills its s and p subshells with eight electrons. Argon, element eighteen, has two electrons in the K shell, eight in the L shell, and eight in the M shell. The fourth period begins again with potassium and calcium, but there is a difference here. After the addition of the 4s electrons and before the addition of the 4p electrons, the sequence goes back to the third energy level to insert electrons in a d shell.
The shells or energy levels are numbered or lettered, beginning with K. So K is one, L is two, M is three, N is four, O is five, P is six, and Q is seven. As the s shells can only have two electrons and the p shells can only have six electrons, the d shells can have only ten electrons and the f shells can have only fourteen electrons. The sequence of addition of the electrons as the atomic number increases is as follows with the first number being the shell number, the s, p, d, or f being the type of subshell, and the last number being the number of electrons in the subshell.
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d10 7p6
It is tempting to put an 8s2 at the end of the sequence, but we have no evidence of an R shell. One way to know this sequence is to memorize it. There is a bit of a pattern in it. The next way to know this sequence is to SEE IT ON THE PERIODIC CHART. As you go from hydrogen down the chart, the Groups 1 and 2 represent the filling of an s subshell. The filling of a p subshell is shown in Groups 3 through 8. The filling of a d subshell is represented by the transition elements (ten elements), and the filling of an fsubshell is shown in the lanthanide and actinide series (fourteen elements).
Here is a copy of the periodic chart as you have usually seen it.
And here is the same chart re-arranged with the Lanthanides and Actinides in their right place and Group I and II afterward. Both of these charts are color coded so that the elements with the 2s subshell on the outside (H and He) are turquoise. All other elements with an s subshell on the outside (Groups I and II) are outlined in blue. Lanthanides and actinides are in grey. Other transition elements are in yellow, and all of the elements that have a p subshell as the last one on the outside are in salmon color.
You may be able to see it better with the subshell areas labeled.
There are several other schemes to help you remember the sequence.
The shape of the s subshells is spherical. The shape of the p subshells is the shape of three barbells at ninety degrees to each other. The shape of the d and f subshells is very complex.
Electron configuration is the "shape" of the electrons around an atom, that is, which energy level (shell) and what kind of orbital it is in. The shells were historically named for the chemists who found and calculated the existence of the first (inner) shells. Their names began with "K" for the first shell, then "L," then "M," so subsequent energy levels were continued up the alphabet. The numbers one through seven have since been substituted for the letters. Notice that I have included an "R" shell (#8) that is purely fantasy but makes the chart symmetrical.
The electron configuration is written out with the first (large) number as the shell number. The letter is the orbital type (either s, p, d, or f). The smaller superscript number is the number of electrons in that orbital.
Use this scheme as follows. You first must know the orbitals. An s orbital only has 2 electrons. A p orbital has six electrons. A d orbital has 10 electrons. An f orbital has 14 electrons. You can tell what type of orbital it is by the number on the chart. The only exception to that is that "8" on the chart is "2" plus "6," that is, an s and a p orbital. The chart reads from left-to-right and then down to the next line, just as English writing. Any element with over 20 electrons in the electrically neutral unattached atom will have all the electrons in the first row on the chart. For instance, scandium, element #21, will have all the electrons in the first row and one from the second. The electron configuration of scandium is: 1s2 2s2 2p6 3s2 3p6 4s2 3d1 Notice that the 2s2 2p6 and 3s2 3p6 came from the eights on the chart (2+6). Notice that the other electron must be taken from the next spot on the chart and that the next spot is the first spot on the left in the next row. It is a 3d spot due to the "10" there and only one more electron is needed, hence 3d1.
The totals on the right indicate using whole rows. If an element has an atomic number over thirty-eight, take all the first two rows and whatever more from the third row. Iodine is number fifty-three. For its electron configuration you would use all the electrons in the first two rows and fifteen more electrons. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 from the first two rows and 4d10 5p5 from the third row. You can add up the totals for each shell at the bottom. Full shells would give you the totals on the bottom.
We have included an R shell (#8) even though there is no such thing yet proven to exist. The chart appears more symmetrical with that shell included. The two electrons from the R shell are in parentheses. We have not yet even made elements that have electrons in the p subshell of the Q shell.
Back to the beginning of Atomic Structure.
ELECTRON CONFIGURATION CHART
K
L
M
N
O
P
Q
R
1
2
3
4
5
6
7
8
s
sp
spd
spdf
spdf
spd
sp
s
2
8
8
2
20
10
6
2
38
10
6
2
56
14
10
6
2
88
14
10
6
2
------------
------------
------------
------------
------------
------------
-----------
------------
2
8
18
32
32
18
8
2
TOTALS
Here is another way to consider the same scheme. The inert elements appear at the end of either the first two, an eight, a six. Wherever there is the six of a p subshell there is the two of an s subshell above it to make eight electrons in the outer full shell of a noble gas. The electron configuration for xenon is:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6
ELECTRON CONFIGURATION CHART
K
L
M
N
O
P
Q
R
1
2
3
4
5
6
7
8
s
sp
spd
spdf
spdf
spd
sp
s
2 /HELIUM
8 /NEON
8 /ARGON
2
20
10
6 /KRYPTON
2
38
10
6 /XENON
2
56
14
10
6 /RADON
2
88
14
10
6 /UND
2
------------
------------
------------
------------
------------
-----------
------------
------------
2
8
18
32
32
18
8
2
TOTALS
?Und? is the undiscovered inert element that would be below radon on the periodic chart.
Another type of electron configuration chart is below. These are more commonly known schemes. All you have to do is follow the arrows through the points to find the sequence. Add up the number of electrons as you go, and stop when you have equaled or almost exceeded the number. There have been a large number of variations on this idea, but they all work the same. Arrange the subshells in a slanted order and go through the array in straight lines, as in the first scheme, or arrange the subshells in a straight line and go through the array in slanted lines, as in the second scheme. In these schemes the inert elements appear after the first s subshell and after every p subshell. As the other type, this scheme type has its advantages and disadvantages, but they all lead to the same sequence.
Back to the beginning of Atomic Structure.
COMMON ELECTRON CONFIGURATION SCHEME A
---?
1s2
---?
2s2
---?
2p6
---?
3s2
---?
3p6
---?
4s2
3d10
---?
4p6
---?
5s2
4d10
---?
5p6
---?
6s2
4f14
---?
5d10
---?
6p6
---?
7s2
5f14
---?
6d10
---?
7p6
COMMON ELECTRON CONFIGURATION SCHEME B
Any of these schemes, if used correctly, will give you the same thing, the sequence of the addition of the electrons to the shells. This pattern is correct for all of the elements that are not Transitional Elements or Lanthanides or Actinides. Of the Transitional Elements and Lanthanides and Actinides about one third of the elements do not follow the pattern. The Periodic Chart below is arranged sideways to show the electron configuration by shell. As you work with the schemes for finding the electron configuration of elements, you can check to see if your answer is correct by adding the electrons in each shell (downwards in the first scheme) and comparing with the Sideways Periodic Chart. The elements that do not fit the pattern have an asterisk by them. In the Transition Elements that do not follow the scheme, only the s subshell of the outer shell and the d subshell of the next to last shell have some trading between them. In the Lanthanide and Actinide series any trading of electrons are between the d subshell of the next to last shell and the f subshell of the second to last shell, the one filling as the elements progress up that series.
Back to the beginning of Atomic Structure.
THE OCTET RULE AS SEEN ON THE PERIODIC CHART
The octet rule states that atoms are most stable when they have a full shell of electrons in the outside electron ring. The first shell has only two electrons in a single s subshell. Helium has a full shell, so it is stable, an inert element. Hydrogen, though, has only one electron. It can lose an electron to become H+, a hydrogen ion or it can gain an electron to become H-, a hydride ion. All the other shells have an s and a p subshell, giving them at least eight electrons on the outside. The s and p subshells often are the only valence electrons, thus the octet rule is named for the eight s and p electrons.
On the Periodic Chart with shell totals you can easily see the octet rule. A valence is a likely charge on an element ion. All of the Group 1 elements have one electron in the outside shell and they all have a valence of plus one. Group 1 elements will lose one and only one electron, that single outside electron to become a single positive ion with a full electron shell of eight electrons (an octet) in the s and p subshells under it.
Group 2 elements all have two electrons in the outer shell and all have a valence of plus two. Beryllium can be a bit different about this, but all other Group 2 elements can lose two electrons to become +2 ions. They do not lose only one electron, but two or none.
The Transition Elements, Lanthanides, and Actinides are all metals. Many of them have varying valences because they can trade around electrons from the outer shell to the inner d or f subshells that are not filled. For this reason they sometimes appear to violate the octet rule.
Group 3 elements have a valence of plus three. Boron is a bit of an exception to this because it is so small it tends to bond covalently. Aluminum has a valence of +3, but some of the larger Group 3 elements have more than one valence.
The smallest Group 4 elements, carbon and silicon, are non-metals because the four electrons are difficult to lose the entire four electrons in the outer shell. Small Group 4 elements tend to make only covalent bonds, sharing electrons. Larger Group 4 elements have more than one valence, usually including +4.
Small Group 5 elements, nitrogen and phosphorus, are non-metals. They tend to either gain three electrons to make an octet or bond covalently. The larger Group 5 elements have more metallic character.
Small Group 6 elements, oxygen and sulfur, tend to either gain two electrons or bond covalently. The larger Group 6 elements have more metallic character.
Group 7 elements all have seven electrons in the outer shell and either gain one electron to become a -1 ion or they make one covalent bond. The Group 7 elements are diatomic gases due to the strong tendency to bond to each other with a covalent bond.
All of the inert elements, the noble gases, have a full octet in the outside shell (or two in the first shell) and so do not naturally combine chemically with other elements.
Back to the beginning of Atomic Structure.
SIDEWAYS PERIODIC CHART WITH ELECTRON SHELL NUMBERS
Fr #87
Cs #55
Rb #37
K #19
Na #11
Li #3
H#1
2 8 18 32 18 8 1
2 8 18 18 8 1
2 8 18 8 1
2 8 8 1
2 8 1
2 1
1
Ra #88
Ba#56
Sr #38
Ca #20
Mg#12
Be #4
2 8 18 32 18 8 2
2 8 18 18 8 2
2 8 18 8 2
2 8 8 2
2 8 2
2 2
Ac #89
La #57
Lr #103
Lu #71
Y #39
Sc #21
2 8 18 32 18 9 2*
2 8 18 18 9 2 *
2 8 18 32 32 9 2
2 8 18 32 9 2
2 8 18 9 2
2 8 9 2
Th #90
Ce #58
Db#104
Hf #72
Zr #40
Ti #22
28 18 32 18 10 2*
2 8 18 19 9 2 *
28 18 32 32 10 2
2 8 18 32 10 2
2 8 18 10 2
2 8 10 2
Pa #91
Pr #59
Jl #105
Ta #73
Nb #41
V #23
2 8 18 32 20 9 2*
2 8 18 21 8 2
28 18 32 32 11 2
2 8 18 32 11 2
2 8 18 12 1 *
2 8 11 2
U #92
Nd#60
Rf#106
W #74
Mo #42
Cr #24
2 8 18 32 21 9 2*
2 8 18 22 8 2
28 18 32 32 12 2
2 8 18 32 12 2
2 8 18 13 1 *
2 8 13 1 *
Np#93
Pm#61
Bh#107
Re#75
Tc #43
Mn #25
2 8 18 32 22 9 2*
2 8 18 23 8 2
28 18 32 32 13 2
2 8 18 32 13 2
2 8 18 13 2
2 8 13 2
Pu#94
Sm#62
Hn#108
Os#76
Ru #44
Fe #26
2 8 18 32 24 8 2
2 8 18 24 8 2
2 8 18 32 32 14 2
28 18 32 14 2
2 8 18 15 1 *
2 8 14 2
Am#95
Eu#63
Mt#109
Ir #77
Rh #45
Co #27
2 8 18 32 25 8 2
2 8 18 25 8 2
28 18 32 32 15 2
2 8 18 32 15 2
2 8 18 16 1 *
2 8 15 2
Cm#96
Gd#64
#110
Pt #78
Pd #46
Ni #28
2 8 18 32 25 9 2*
2 8 18 25 9 2 *
28 18 32 17 1 *
2 8 18 18 0 *
2 8 16 2
Bk #97
Tb #65
#111
Au#79
Ag #47
Cu#29
2 8 18 32 26 9 2*
2 8 18 27 8 2
28 18 32 18 1 *
2 8 18 18 1 *
2 8 18 1 *
Cf #98
Dy #66
#112
Hg#80
Cd #48
Zn #30
2 8 18 32 28 8 2
2 8 18 28 8 2
2 8 18 32 18 2
2 8 18 18 2
2 8 18 2
Es #99
Ho #67
#113
Tl #81
In #49
Ga #31
Al #13
B #5
2 8 18 32 29 8 2
2 8 18 29 8 2
2 8 18 32 18 3
2 8 18 18 3
2 8 18 3
2 8 3
2 3
Fm#100
Er #68
#114
Pb #82
Sn #50
Ge #32
Si #14
C #6
2 8 18 32 30 8 2
2 8 18 30 8 2
2 8 18 32 18 4
2 8 18 18 4
2 8 18 4
2 8 4
2 4
Md#101
Tm#69
#115
Bi #83
Sb #51
As #33
P #15
N #7
2 8 18 32 31 8 2
2 8 18 31 8 2
2 8 18 32 18 5
2 8 18 18 5
2 8 18 5
2 8 5
2 5
No#102
Yb #70
#116
Po #84
Te #52
Se #34
S #16
O #8
2 8 18 32 32 8 2
2 8 18 32 8 2
2 8 18 32 18 6
2 8 18 18 6
2 8 18 6
2 8 6
2 6
#117
At#85
I #53
Br #35
Cl #17
F #9
2 8 18 32 18 7
2 8 18 18 7
2 8 18 7
2 8 7
2 7
#118
Rn#86
Xe#54
Kr #36
Ar #18
Ne#10
He#2
2 8 18 32 18 8
2 8 18 18 8
2 8 18 8
2 8 8
2 8
2
Back to the beginning of Atomic Structure.
LEWIS STRUCTURES OF THE ELEMENTS
Examine the Sideways Periodic Chart With Electron Shell Numbers again. All of the Group I elements and hydrogen (the top row of the chart) have one and only one electron in the outside shell. That single electron is what gives these elements the distinctive character of the group. The Lewis structures are just an attempt to show these valence electrons in a graphic manner as they are used to combine with other elements. The element symbol is in the center and as many as four groups of two electrons are shown as dots above, below, to the right and left of the element symbol to show the valence electrons. All of the inert gases (noble gases) have all eight of the electrons around the element symbol, except for helium, which has only two electrons even with a full shell. Below is a demonstration of the noble gases written in Lewis structure. Notice the electrons are in red just to emphasize them.
All the other elements have less than eight electrons in the outside shell. These electrons can be in the positions of the eight electrons of the noble gases, but there are some suggestions about where they belong. The Group I elements have only one electron in the outer shell, so it really does not matter where the electron dot is placed, over, under, right or left of the element symbol.
Group II elements have two electrons. Some authors will place the two electron dots together on any side of the element symbol because the electrons really are in an s subshell together.
Some authors will show the electrons separated from each other in any of the two positions with only one electron in each position. The reasoning behind that is that the electrons really do try to move as far away from each other as possible.
Boron and the elements below it on the periodic table all have three electrons in the outside shell. These electrons may be grouped as each electron alone in one of the positions around the element symbol or as a group of two (s) electrons in one position and one electron in another. Boron is usually shown with separate electrons because it bonds mostly covalently. Covalent bonds, we know from the shape of molecules, tend to blend the s and p subshells into sp orbitals with one s and one p orbital blended, sp2 orbitals with one s and two p orbitals blended, or sp3 orbitals, using the single s orbital with all three p orbitals. The sp2 orbitals of boron tend to be flat trigonal shape, that is, the bonds are at 120 degrees from each other in a flat circle around the boron atom in the center. The Lewis structure of boron is any of the shapes below.
Carbon and the elements below it have four electrons in the outer shell. Carbon and silicon are usually shown in Lewis structures to have four separated electrons, again because these elements bond purely with covalent bonds. The sp3 orbitals of carbon and silicon are tetrahedral in shape.
Nitrogen and the elements below it have five electrons in the valence shell, so they must be shown with one pair (anywhere) and three solitary electrons.
Oxygen and the elements below it have six valence electrons and so must have two pairs and two solitary electrons.
Elements in the halogen group, Group VII, all have seven electrons in the outer shell, so only there are three groups of two and a single electron in the last position.
The transition elements and the Lanthanide and Actinide series elements are not often used in the covalent bonds that the Lewis structures usually portray, but these metal elements can be portrayed in this manner using the number of electrons in the outer shell that corresponds with the valence of the element.
In using the Lewis structures to show covalent bonds, the pair of electrons that are in the bond are shown as a dashed line. For example, ammonia would be shown with the bonds from the nitrogen to the hydrogens and the unshared pair of electrons on the nitrogen.
The covalent bond dash is in red in the above sketch also. Notice that the electrons from all of the participants in this molecule are all accounted for.
There is more on Lewis structures in the compounds chapter in Chemtutor.
Back to the beginning of Atomic Structure.
Heuristics Numbers and MathUnits and MeasuresElementsPeriodic TableStates of MatterCompoundsReactionsMols, Stoichiometry, and PercentsOxidation and Reduction Reactions GasesSolutionsAcids and basesKineticsThermochemistry
[Frequently Asked Questions] [Links Page] [About Us] [Contact Us]
Copyright ? 1997-2005 Chemtutor, LLC. All rights reserved.
Publication of any part is prohibited without prior written consent, except for instructor use publishing for instructor's own classroom students. All hard copy materials distributed under this exception must have on every page distributed reference to http://www.chemtutor.com as source. Under the same exception granted to classroom teachers, full recognition of Chemtutor must be given when all or any part is included in any other electronic representation, such as a web site, whether by direct inclusion or by hyperlink.
ATOMIC STRUCTURE
And you thought you were strangeAtomic weights and atomic numbers.Formula weight or molecular weight.Electron configuration.Electron configuration chart.Common electron configuration scheme.Octet rule as seen on the periodic chart.Sideways periodic chart with electron shell numbers.Lewis structures of elements.
AND YOU THOUGHT YOU WERE STRANGE
Here is an outrageous thought: All the matter around you is made of atoms, and all atoms are made of only three types of subatomic particle, protons, electrons, and neutrons. Furthermore, all protons are exactly the same, all neutrons are exactly the same, and all electrons are exactly the same. Protons and neutrons have almost exactly the same mass. Electrons have a mass that is about 1/1835 the mass of a proton. Electrons have a unit negative charge. Protons each have a positive charge. These charges are genuine electrical charges. Neutrons do not have any charge.
Even more outrageous is the shape of the atoms with the three subatomic particles. The neutrons and protons are in the center of the atom in a nucleus. The electrons are outside the nucleus in electron shells that are in different shapes at different distances from the nucleus. The atom is mostly empty space. Ernest Rutherford shot subatomic particles at a very thin piece of gold. Most of the particles went straight through the gold. It was like shooting a rifle into a thin line of trees. Some of the particles bounced off, some stuck inside, but the major portion of them passed through the gold foil. By Rutherford?s calculations, the nucleus in an atom is like a B-B in a boxcar. That is a genuinely outrageous idea. Almost all the mass of an atom is concentrated in the tiny nucleus. The mass of a proton or neutron is 1.66 E -24 grams or one AMU, atomic mass unit. The mass of an electron is 9.05 E -28 grams. This number is a billionth of a billionth of a billionth of a gram. It is not possible for anyone or any machine that uses light to actually see a proton using visible light. The wavelength of light is too large to be able to detect anything that small.
Back to the beginning of Atomic Structure.
ATOMIC WEIGHTS AND ATOMIC NUMBERS
The integer that you find in each box of the Periodic Chart is the atomic number. The atomic number is the number of protons in the nucleus of each atom. Another number that you can often find in the box with the symbol of the element is not an integer. It is oversimplifying only a little to say that this number is the number of protons plus the average number of neutrons in that element. The number is called the atomic weight or atomic mass.
How can it be that an element must have an averaged atomic weight? The number of protons defines the type of element. If an atom has six protons, it is carbon. If it has 92 protons, it is uranium. The number of neutrons in the nucleus of an element can be different, though. Carbon 12 is the commonest type of carbon. Carbon 12 has six protons (naturally, otherwise it wouldn?t be carbon) and six neutrons. The mass of the electrons is negligible. Carbon 12 has a mass of twelve. Carbon 13 has six protons and seven neutrons. Carbon 14 has six protons and eight neutrons. Carbon 14 is radioactive because, as other atoms with the wrong percentage of neutrons to protons, it is unstable. The nucleus tends to pop apart. The proper ratio of protons to neutrons is about one to one for small elements and about one proton to one and a half neutrons for the larger elements. Types of an element in which every atom has the same number of protons and the same number of neutrons are called isotopes. Carbon 14 is a radioactive isotope of carbon. Any carbon 14 that was made at the time the earth was formed is now almost all gone. Carbon 14 is continuously made from high energy electromagnetic radiation hitting nitrogen atoms in the ozone layer of the earth. This carbon 14 when taken into plants as CO2 will also be taken into animals. We can find out how much carbon 14 that normally is in a living plant or animal and from there we can find the actual amount of carbon 14 left in a plant or animal long dead. We can get a very good idea of how long ago that plant or animal was living from the amount of carbon 14 remaining in the dead body. This process is called ?carbon dating.? The stable, non-radioactive isotopes of carbon play no part in this. As a whole element, carbon has a more or less fixed proportion of the various carbon isotopes. For this reason, we can determine a weighted average of the isotopes for all elements. On a periodic chart you may see some atomic weights that are integers or in parentheses. These are usually on the very large or very rare or very radioactive elements. That is not really an integer atomic weight, but the atomic weight has been estimated to the nearest integer.
Back to the beginning of Atomic Structure.
FORMULA WEIGHT OR MOLECULAR WEIGHT OR FORMULA MASS OR MOLAR MASS
Now with the atomic weight information we can consider matching up atoms on a mass-to-mass basis. Let?s take hydrogen chloride, HCl. One hydrogen atom is attached to one chlorine atom, but they have different masses. A hydrogen atom has a mass of 1.008 AMU and a chlorine atom has a mass of 35.453 AMU. Practically speaking, one AMU is far too small a mass for us to weigh in the lab. We could weigh 1.008 grams of hydrogen and 35.453 grams of chlorine, and they would match up exactly right. There would be the same number of hydrogen atoms as chlorine atoms. They could join together to make HCl with no hydrogen or chlorine left over. If we take one gram of a material for every AMU of mass in the atoms of just one of them, we will have a mol (or mole) of that material. One mol of any material, therefore, has the same number of particles of the material named, this number being Avogadro?s number, 6.022 E 23.
The formula weight is the most general term that includes atomic weight and molecular weight. In the case of the HCl, we can add the atomic weights of the elements in the compound and get a molecular weight. The molecular weight of HCl is 36.461 g/mol, the sum of the atomic weights of hydrogen and chlorine. The unit of molecular weight is grams per mol. The way to calculate the molecular weight of any formula is to add up the atomic weights of all the atoms in the formula. CuSO4?5H2O is copper II sulfate pentahydrate. The formula has one copper atom, one sulfur atom, nine oxygen atoms, and ten hydrogen atoms. To get the formula weight of this compound we would add up the atomic weights. Copper II sulfate pentahydrate is not a molecule, strictly speaking, but you will hear the term ?molecular weight? used for it rather than the more proper ?formula weight.' Since the unit of formula weight is grams per mol, it makes good sense to use the formula weight of a material as a conversion factor between the mass of a material and the number of mols of the material.
Back to the beginning of Atomic Structure.
ELECTRON CONFIGURATION
Protons have a positive charge and electrons have a negative charge. Free (unattached) uncharged atoms have the same number of electrons as protons to be electrically neutral. The protons are in the nucleus and do not change or vary except in some nuclear reactions. The electrons are in discrete pathways or shells around the nucleus. There is a ranking or heirarchy of the shells, usually with the shells further from the nucleus having a higher energy. As we consider the electron configuration of atoms, we will be describing the ground state position of the electrons. When electrons have higher energy, they may move up away from the nucleus into higher energy shells. As we consider the electron configuration, we will be describing the ground state positions of the electrons.
A hydrogen atom has only one proton and one electron. The electron of a hydrogen atom travels around the proton nucleus in a shell of a spherical shape. The two electrons of helium, element number two, are in the same spherical shape around the nucleus. The first shell only has one subshell, and that subshell has only one orbital, or pathway for electrons. Each orbital has a place for two electrons. The spherical shape of the lone orbital in the first energy level has given it the name ?s? orbital. Helium is the last element in the first period. Being an inert element, it indicates that that shell is full. Shell number one has only one s subshell and all s subshells have only one orbital. Each orbital only has room for two electrons. So the first shell, called the K shell, has only two electrons.
Beginning with lithium, the electrons do not have room in the first shell or energy level. Lithium has two electrons in the first shell and one electron in the next shell. The first shell fills first and the others more or less in order as the element size increases up the Periodic Chart, but the sequence is not immediately obvious. The second energy level has room for eight electrons. The second energy level has not only an s orbital, but also a p subshell with three orbitals. The p subshell can contain six electrons. The p subshell has a shape of three dumbbells at ninety degrees to each other, each dumbbell shape being one orbital. With the s and p subshells the second shell, the L shell, can hold a total of eight electrons. You can see this on the periodic chart. Lithium has one electron in the outside shell, the L shell. Beryllium has two electrons in the outside shell. The s subshell fills first, so all other electrons adding to this shell go into the p subshell. Boron has three outside electrons, carbon has four, nitrogen has five, oxygen has six, and fluorine has seven. Neon has a full shell of eight electrons in the outside shell, the L shell, meaning the neon is an inert element, the end of the period.
Beginning again at sodium with one electron in the outside shell, the M shell fills its s and p subshells with eight electrons. Argon, element eighteen, has two electrons in the K shell, eight in the L shell, and eight in the M shell. The fourth period begins again with potassium and calcium, but there is a difference here. After the addition of the 4s electrons and before the addition of the 4p electrons, the sequence goes back to the third energy level to insert electrons in a d shell.
The shells or energy levels are numbered or lettered, beginning with K. So K is one, L is two, M is three, N is four, O is five, P is six, and Q is seven. As the s shells can only have two electrons and the p shells can only have six electrons, the d shells can have only ten electrons and the f shells can have only fourteen electrons. The sequence of addition of the electrons as the atomic number increases is as follows with the first number being the shell number, the s, p, d, or f being the type of subshell, and the last number being the number of electrons in the subshell.
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d10 7p6
It is tempting to put an 8s2 at the end of the sequence, but we have no evidence of an R shell. One way to know this sequence is to memorize it. There is a bit of a pattern in it. The next way to know this sequence is to SEE IT ON THE PERIODIC CHART. As you go from hydrogen down the chart, the Groups 1 and 2 represent the filling of an s subshell. The filling of a p subshell is shown in Groups 3 through 8. The filling of a d subshell is represented by the transition elements (ten elements), and the filling of an fsubshell is shown in the lanthanide and actinide series (fourteen elements).
Here is a copy of the periodic chart as you have usually seen it.
And here is the same chart re-arranged with the Lanthanides and Actinides in their right place and Group I and II afterward. Both of these charts are color coded so that the elements with the 2s subshell on the outside (H and He) are turquoise. All other elements with an s subshell on the outside (Groups I and II) are outlined in blue. Lanthanides and actinides are in grey. Other transition elements are in yellow, and all of the elements that have a p subshell as the last one on the outside are in salmon color.
You may be able to see it better with the subshell areas labeled.
There are several other schemes to help you remember the sequence.
The shape of the s subshells is spherical. The shape of the p subshells is the shape of three barbells at ninety degrees to each other. The shape of the d and f subshells is very complex.
Electron configuration is the "shape" of the electrons around an atom, that is, which energy level (shell) and what kind of orbital it is in. The shells were historically named for the chemists who found and calculated the existence of the first (inner) shells. Their names began with "K" for the first shell, then "L," then "M," so subsequent energy levels were continued up the alphabet. The numbers one through seven have since been substituted for the letters. Notice that I have included an "R" shell (#8) that is purely fantasy but makes the chart symmetrical.
The electron configuration is written out with the first (large) number as the shell number. The letter is the orbital type (either s, p, d, or f). The smaller superscript number is the number of electrons in that orbital.
Use this scheme as follows. You first must know the orbitals. An s orbital only has 2 electrons. A p orbital has six electrons. A d orbital has 10 electrons. An f orbital has 14 electrons. You can tell what type of orbital it is by the number on the chart. The only exception to that is that "8" on the chart is "2" plus "6," that is, an s and a p orbital. The chart reads from left-to-right and then down to the next line, just as English writing. Any element with over 20 electrons in the electrically neutral unattached atom will have all the electrons in the first row on the chart. For instance, scandium, element #21, will have all the electrons in the first row and one from the second. The electron configuration of scandium is: 1s2 2s2 2p6 3s2 3p6 4s2 3d1 Notice that the 2s2 2p6 and 3s2 3p6 came from the eights on the chart (2+6). Notice that the other electron must be taken from the next spot on the chart and that the next spot is the first spot on the left in the next row. It is a 3d spot due to the "10" there and only one more electron is needed, hence 3d1.
The totals on the right indicate using whole rows. If an element has an atomic number over thirty-eight, take all the first two rows and whatever more from the third row. Iodine is number fifty-three. For its electron configuration you would use all the electrons in the first two rows and fifteen more electrons. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 from the first two rows and 4d10 5p5 from the third row. You can add up the totals for each shell at the bottom. Full shells would give you the totals on the bottom.
We have included an R shell (#8) even though there is no such thing yet proven to exist. The chart appears more symmetrical with that shell included. The two electrons from the R shell are in parentheses. We have not yet even made elements that have electrons in the p subshell of the Q shell.
Back to the beginning of Atomic Structure.
ELECTRON CONFIGURATION CHART
K
L
M
N
O
P
Q
R
1
2
3
4
5
6
7
8
s
sp
spd
spdf
spdf
spd
sp
s
2
8
8
2
20
10
6
2
38
10
6
2
56
14
10
6
2
88
14
10
6
2
------------
------------
------------
------------
------------
------------
-----------
------------
2
8
18
32
32
18
8
2
TOTALS
Here is another way to consider the same scheme. The inert elements appear at the end of either the first two, an eight, a six. Wherever there is the six of a p subshell there is the two of an s subshell above it to make eight electrons in the outer full shell of a noble gas. The electron configuration for xenon is:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6
ELECTRON CONFIGURATION CHART
K
L
M
N
O
P
Q
R
1
2
3
4
5
6
7
8
s
sp
spd
spdf
spdf
spd
sp
s
2 /HELIUM
8 /NEON
8 /ARGON
2
20
10
6 /KRYPTON
2
38
10
6 /XENON
2
56
14
10
6 /RADON
2
88
14
10
6 /UND
2
------------
------------
------------
------------
------------
-----------
------------
------------
2
8
18
32
32
18
8
2
TOTALS
?Und? is the undiscovered inert element that would be below radon on the periodic chart.
Another type of electron configuration chart is below. These are more commonly known schemes. All you have to do is follow the arrows through the points to find the sequence. Add up the number of electrons as you go, and stop when you have equaled or almost exceeded the number. There have been a large number of variations on this idea, but they all work the same. Arrange the subshells in a slanted order and go through the array in straight lines, as in the first scheme, or arrange the subshells in a straight line and go through the array in slanted lines, as in the second scheme. In these schemes the inert elements appear after the first s subshell and after every p subshell. As the other type, this scheme type has its advantages and disadvantages, but they all lead to the same sequence.
Back to the beginning of Atomic Structure.
COMMON ELECTRON CONFIGURATION SCHEME A
---?
1s2
---?
2s2
---?
2p6
---?
3s2
---?
3p6
---?
4s2
3d10
---?
4p6
---?
5s2
4d10
---?
5p6
---?
6s2
4f14
---?
5d10
---?
6p6
---?
7s2
5f14
---?
6d10
---?
7p6
COMMON ELECTRON CONFIGURATION SCHEME B
Any of these schemes, if used correctly, will give you the same thing, the sequence of the addition of the electrons to the shells. This pattern is correct for all of the elements that are not Transitional Elements or Lanthanides or Actinides. Of the Transitional Elements and Lanthanides and Actinides about one third of the elements do not follow the pattern. The Periodic Chart below is arranged sideways to show the electron configuration by shell. As you work with the schemes for finding the electron configuration of elements, you can check to see if your answer is correct by adding the electrons in each shell (downwards in the first scheme) and comparing with the Sideways Periodic Chart. The elements that do not fit the pattern have an asterisk by them. In the Transition Elements that do not follow the scheme, only the s subshell of the outer shell and the d subshell of the next to last shell have some trading between them. In the Lanthanide and Actinide series any trading of electrons are between the d subshell of the next to last shell and the f subshell of the second to last shell, the one filling as the elements progress up that series.
Back to the beginning of Atomic Structure.
THE OCTET RULE AS SEEN ON THE PERIODIC CHART
The octet rule states that atoms are most stable when they have a full shell of electrons in the outside electron ring. The first shell has only two electrons in a single s subshell. Helium has a full shell, so it is stable, an inert element. Hydrogen, though, has only one electron. It can lose an electron to become H+, a hydrogen ion or it can gain an electron to become H-, a hydride ion. All the other shells have an s and a p subshell, giving them at least eight electrons on the outside. The s and p subshells often are the only valence electrons, thus the octet rule is named for the eight s and p electrons.
On the Periodic Chart with shell totals you can easily see the octet rule. A valence is a likely charge on an element ion. All of the Group 1 elements have one electron in the outside shell and they all have a valence of plus one. Group 1 elements will lose one and only one electron, that single outside electron to become a single positive ion with a full electron shell of eight electrons (an octet) in the s and p subshells under it.
Group 2 elements all have two electrons in the outer shell and all have a valence of plus two. Beryllium can be a bit different about this, but all other Group 2 elements can lose two electrons to become +2 ions. They do not lose only one electron, but two or none.
The Transition Elements, Lanthanides, and Actinides are all metals. Many of them have varying valences because they can trade around electrons from the outer shell to the inner d or f subshells that are not filled. For this reason they sometimes appear to violate the octet rule.
Group 3 elements have a valence of plus three. Boron is a bit of an exception to this because it is so small it tends to bond covalently. Aluminum has a valence of +3, but some of the larger Group 3 elements have more than one valence.
The smallest Group 4 elements, carbon and silicon, are non-metals because the four electrons are difficult to lose the entire four electrons in the outer shell. Small Group 4 elements tend to make only covalent bonds, sharing electrons. Larger Group 4 elements have more than one valence, usually including +4.
Small Group 5 elements, nitrogen and phosphorus, are non-metals. They tend to either gain three electrons to make an octet or bond covalently. The larger Group 5 elements have more metallic character.
Small Group 6 elements, oxygen and sulfur, tend to either gain two electrons or bond covalently. The larger Group 6 elements have more metallic character.
Group 7 elements all have seven electrons in the outer shell and either gain one electron to become a -1 ion or they make one covalent bond. The Group 7 elements are diatomic gases due to the strong tendency to bond to each other with a covalent bond.
All of the inert elements, the noble gases, have a full octet in the outside shell (or two in the first shell) and so do not naturally combine chemically with other elements.
Back to the beginning of Atomic Structure.
SIDEWAYS PERIODIC CHART WITH ELECTRON SHELL NUMBERS
Fr #87
Cs #55
Rb #37
K #19
Na #11
Li #3
H#1
2 8 18 32 18 8 1
2 8 18 18 8 1
2 8 18 8 1
2 8 8 1
2 8 1
2 1
1
Ra #88
Ba#56
Sr #38
Ca #20
Mg#12
Be #4
2 8 18 32 18 8 2
2 8 18 18 8 2
2 8 18 8 2
2 8 8 2
2 8 2
2 2
Ac #89
La #57
Lr #103
Lu #71
Y #39
Sc #21
2 8 18 32 18 9 2*
2 8 18 18 9 2 *
2 8 18 32 32 9 2
2 8 18 32 9 2
2 8 18 9 2
2 8 9 2
Th #90
Ce #58
Db#104
Hf #72
Zr #40
Ti #22
28 18 32 18 10 2*
2 8 18 19 9 2 *
28 18 32 32 10 2
2 8 18 32 10 2
2 8 18 10 2
2 8 10 2
Pa #91
Pr #59
Jl #105
Ta #73
Nb #41
V #23
2 8 18 32 20 9 2*
2 8 18 21 8 2
28 18 32 32 11 2
2 8 18 32 11 2
2 8 18 12 1 *
2 8 11 2
U #92
Nd#60
Rf#106
W #74
Mo #42
Cr #24
2 8 18 32 21 9 2*
2 8 18 22 8 2
28 18 32 32 12 2
2 8 18 32 12 2
2 8 18 13 1 *
2 8 13 1 *
Np#93
Pm#61
Bh#107
Re#75
Tc #43
Mn #25
2 8 18 32 22 9 2*
2 8 18 23 8 2
28 18 32 32 13 2
2 8 18 32 13 2
2 8 18 13 2
2 8 13 2
Pu#94
Sm#62
Hn#108
Os#76
Ru #44
Fe #26
2 8 18 32 24 8 2
2 8 18 24 8 2
2 8 18 32 32 14 2
28 18 32 14 2
2 8 18 15 1 *
2 8 14 2
Am#95
Eu#63
Mt#109
Ir #77
Rh #45
Co #27
2 8 18 32 25 8 2
2 8 18 25 8 2
28 18 32 32 15 2
2 8 18 32 15 2
2 8 18 16 1 *
2 8 15 2
Cm#96
Gd#64
#110
Pt #78
Pd #46
Ni #28
2 8 18 32 25 9 2*
2 8 18 25 9 2 *
28 18 32 17 1 *
2 8 18 18 0 *
2 8 16 2
Bk #97
Tb #65
#111
Au#79
Ag #47
Cu#29
2 8 18 32 26 9 2*
2 8 18 27 8 2
28 18 32 18 1 *
2 8 18 18 1 *
2 8 18 1 *
Cf #98
Dy #66
#112
Hg#80
Cd #48
Zn #30
2 8 18 32 28 8 2
2 8 18 28 8 2
2 8 18 32 18 2
2 8 18 18 2
2 8 18 2
Es #99
Ho #67
#113
Tl #81
In #49
Ga #31
Al #13
B #5
2 8 18 32 29 8 2
2 8 18 29 8 2
2 8 18 32 18 3
2 8 18 18 3
2 8 18 3
2 8 3
2 3
Fm#100
Er #68
#114
Pb #82
Sn #50
Ge #32
Si #14
C #6
2 8 18 32 30 8 2
2 8 18 30 8 2
2 8 18 32 18 4
2 8 18 18 4
2 8 18 4
2 8 4
2 4
Md#101
Tm#69
#115
Bi #83
Sb #51
As #33
P #15
N #7
2 8 18 32 31 8 2
2 8 18 31 8 2
2 8 18 32 18 5
2 8 18 18 5
2 8 18 5
2 8 5
2 5
No#102
Yb #70
#116
Po #84
Te #52
Se #34
S #16
O #8
2 8 18 32 32 8 2
2 8 18 32 8 2
2 8 18 32 18 6
2 8 18 18 6
2 8 18 6
2 8 6
2 6
#117
At#85
I #53
Br #35
Cl #17
F #9
2 8 18 32 18 7
2 8 18 18 7
2 8 18 7
2 8 7
2 7
#118
Rn#86
Xe#54
Kr #36
Ar #18
Ne#10
He#2
2 8 18 32 18 8
2 8 18 18 8
2 8 18 8
2 8 8
2 8
2
Back to the beginning of Atomic Structure.
LEWIS STRUCTURES OF THE ELEMENTS
Examine the Sideways Periodic Chart With Electron Shell Numbers again. All of the Group I elements and hydrogen (the top row of the chart) have one and only one electron in the outside shell. That single electron is what gives these elements the distinctive character of the group. The Lewis structures are just an attempt to show these valence electrons in a graphic manner as they are used to combine with other elements. The element symbol is in the center and as many as four groups of two electrons are shown as dots above, below, to the right and left of the element symbol to show the valence electrons. All of the inert gases (noble gases) have all eight of the electrons around the element symbol, except for helium, which has only two electrons even with a full shell. Below is a demonstration of the noble gases written in Lewis structure. Notice the electrons are in red just to emphasize them.
All the other elements have less than eight electrons in the outside shell. These electrons can be in the positions of the eight electrons of the noble gases, but there are some suggestions about where they belong. The Group I elements have only one electron in the outer shell, so it really does not matter where the electron dot is placed, over, under, right or left of the element symbol.
Group II elements have two electrons. Some authors will place the two electron dots together on any side of the element symbol because the electrons really are in an s subshell together.
Some authors will show the electrons separated from each other in any of the two positions with only one electron in each position. The reasoning behind that is that the electrons really do try to move as far away from each other as possible.
Boron and the elements below it on the periodic table all have three electrons in the outside shell. These electrons may be grouped as each electron alone in one of the positions around the element symbol or as a group of two (s) electrons in one position and one electron in another. Boron is usually shown with separate electrons because it bonds mostly covalently. Covalent bonds, we know from the shape of molecules, tend to blend the s and p subshells into sp orbitals with one s and one p orbital blended, sp2 orbitals with one s and two p orbitals blended, or sp3 orbitals, using the single s orbital with all three p orbitals. The sp2 orbitals of boron tend to be flat trigonal shape, that is, the bonds are at 120 degrees from each other in a flat circle around the boron atom in the center. The Lewis structure of boron is any of the shapes below.
Carbon and the elements below it have four electrons in the outer shell. Carbon and silicon are usually shown in Lewis structures to have four separated electrons, again because these elements bond purely with covalent bonds. The sp3 orbitals of carbon and silicon are tetrahedral in shape.
Nitrogen and the elements below it have five electrons in the valence shell, so they must be shown with one pair (anywhere) and three solitary electrons.
Oxygen and the elements below it have six valence electrons and so must have two pairs and two solitary electrons.
Elements in the halogen group, Group VII, all have seven electrons in the outer shell, so only there are three groups of two and a single electron in the last position.
The transition elements and the Lanthanide and Actinide series elements are not often used in the covalent bonds that the Lewis structures usually portray, but these metal elements can be portrayed in this manner using the number of electrons in the outer shell that corresponds with the valence of the element.
In using the Lewis structures to show covalent bonds, the pair of electrons that are in the bond are shown as a dashed line. For example, ammonia would be shown with the bonds from the nitrogen to the hydrogens and the unshared pair of electrons on the nitrogen.
The covalent bond dash is in red in the above sketch also. Notice that the electrons from all of the participants in this molecule are all accounted for.
There is more on Lewis structures in the compounds chapter in Chemtutor.
Back to the beginning of Atomic Structure.
Heuristics Numbers and MathUnits and MeasuresElementsPeriodic TableStates of MatterCompoundsReactionsMols, Stoichiometry, and PercentsOxidation and Reduction Reactions GasesSolutionsAcids and basesKineticsThermochemistry
[Frequently Asked Questions] [Links Page] [About Us] [Contact Us]
Copyright ? 1997-2005 Chemtutor, LLC. All rights reserved.
Publication of any part is prohibited without prior written consent, except for instructor use publishing for instructor's own classroom students. All hard copy materials distributed under this exception must have on every page distributed reference to http://www.chemtutor.com as source. Under the same exception granted to classroom teachers, full recognition of Chemtutor must be given when all or any part is included in any other electronic representation, such as a web site, whether by direct inclusion or by hyperlink.
What is Chemistry ?
Chemistry, from Greek χημεία khemeia meaning "alchemy", is a branch of science.
Modern chemistry focuses on the study of elements of the world and the bonds between elements.
Also Chemistry deals with composition, structure, and properties of substances and the transformations that they undergo.
In the study of matter, chemistry also investigates its interactions with energy and itself.
Because of the diversity of matter, which is mostly in the form of atoms, chemists often study how atoms of different chemical elements interact to form molecules, and how molecules interact with each other.
Modern chemistry focuses on the study of elements of the world and the bonds between elements.
Also Chemistry deals with composition, structure, and properties of substances and the transformations that they undergo.
In the study of matter, chemistry also investigates its interactions with energy and itself.
Because of the diversity of matter, which is mostly in the form of atoms, chemists often study how atoms of different chemical elements interact to form molecules, and how molecules interact with each other.
Fields of Chemistry
Analytical chemistry: Chromatography, Spectroscopy
Biochemistry: Molecular biology
Environmental chemistry: Geochemistry
Inorganic chemistry: Inorganic reactions
Materials science: Nanotechnology
Medicinal chemistry
Nuclear chemistry
Organic chemistry: Functional groups, Organic compounds, Organic reactions
Organometallic chemistry
Pharmacy
Pharmacology
Physical chemistry: Electrochemistry, Quantum chemistry
Polymer chemistry
Supramolecular chemistry
Theoretical chemistry: Computational chemistry
History and Philosophy of Chemistry
Many chemists have an interest in the history of chemistry.
And those with philosophical interests will be interested in the philosophy of chemistry which has quite recently developed along a path somewhat different from the general philosophy of science.
Other articles that might interest you are:-
Superseded chemistry theories
AlchemyScientific method
There is a Wikipedia Project on the History of Science and portals for the scientific method and philosophy of science.
And those with philosophical interests will be interested in the philosophy of chemistry which has quite recently developed along a path somewhat different from the general philosophy of science.
Other articles that might interest you are:-
Superseded chemistry theories
AlchemyScientific method
There is a Wikipedia Project on the History of Science and portals for the scientific method and philosophy of science.
Chemistry Resources
Wikipedia:WikiProject Chemicals/data is a collection of links and references that are useful for chemistry-related works.
This includes free online chemical databases, publications, patents, computer programs, and various tools.
Students can find the following link interesting for Organic Chemistry
http://www.organicchemistryreview.com/
This includes free online chemical databases, publications, patents, computer programs, and various tools.
Students can find the following link interesting for Organic Chemistry
http://www.organicchemistryreview.com/
Top Chemistry Websites
What's That Stuff?
What exactly is in your toothpaste?
What about that paper you’re writing on or the bug spray you use in summer?
This site puts science into everyday life, with informative descriptions of the chemistry behind the products we use on a regular basis.
Chemistry Comes Alive: Sample Movies - From the Journal of Chemical Education.
Exciting movies of some explosive, flaming, and colorful chemical reactions. You will need the free QuickTime Player to watch.
ChemMatters - Great online resource for High School chemistry teachers brought to you by the American Chemical Society. Pdf versions of "ChemMatters" magazine, geared towards a high school audience, are available online along with the corresponding teachers’ guides.
A Chemical Jigsaw Puzzle - Learning basic chemistry is even more fun when it's a puzzle! Learn the concept of valency and how to balance equations using this fun visual and tactile method.
Food and Science - Students can learn chemistry through cooking! This site for teachers has lots of fun lesson plans that link chemistry and food preparation.
The Periodic Table of Comic Books - Comics and chemistry together? What could be better? Click on an element in the periodic table and see the comics associated with that element.
The pH Factor - This site will help teachers introduce the concepts of acid and base to middle school students. There are lesson plans, classroom activities, and a teachers guide.
Delights of Chemistry - A trip to this site is sure to spark your interest in chemistry. You can watch videos of exciting chemistry demonstrations, view experiments illustrated with photos and complete with explanations, and browse through a chemical reaction photo gallery.
Chembalancer - This online game with visual aids can help beginning chemistry students learn how to balance chemical equations.
Reactive Reports - Learn about exciting developments in chemistry and related fields by checking out this Web-based chemistry magazine.
Read about the molecule behind a Biblical plague, a marine bacteria that can bubble-wrap iron, and a compound found in a Native American herbal remedy that may hold the key to overcoming antibiotic resistance.
The articles are accessible to a lay audience.
The Learning Matters of Chemistry - Check out the "Computer Graphics" section, which has very cool animations of famous experiments and illustrates important principles of chemistry.
Also, visit the "Interactivy" section for a game of "Periodic TableTris"--a Tetris-like game.Simple, Common, and Interesting Molecules - Ever wonder about the three-dimensional chemical structure of aspirin?
How about caffeine?
Check out this site from the Indiana University Molecular Structure Center.
A Visual Interpretation of the Table of Elements - An innovative and elegant visual tour through the periodic table. Each of the 109 elements is accompanied by a visual image, as well as a description and history (including the origin of its name). These pages are image heavy, and take a while to load.
Multimedia Molecule Extravaganza - Explore animated multimedia movies of DNA and other complex molecules. This is an excellent upper level chemistry resource. Requires QuickTime Player.
Reeko's Mad Scientist Lab - This densely packed site has scads and scads of excellent science and chemistry experiments you can try at home, as well as science book reviews, science tips and more, all delivered in a highly irreverent style.-->
Polymers &
Liquid Crystals - A well- constructed and informative site. Learn basic concepts and check out "downloadable" simulations.
The Macrogalleria - Learn about polymers and polymer science. The site really does take you through a mall (hence the "Macrogalleria") to demonstrate how polymers are used in everyday products.
BioChemNet - (now links to High School Hub. There are still many biology and chemistry links)- An impressive collection of links to biology and chemistry sites.
Chemist's Art Gallery -Animations and visualizations of molecules, polymers, cells, etc. I'm not sure what all the molecules and polymers are, but they sure are pretty!
Chemistry Teaching Resources - The most comprehensive listing of chemistry teaching resources we've come across.
Chemicool Periodic Table - A clickable periodic table that gives in-depth information on each element. The most complete periodic table we've seen on the web to date.
WebElements - A clickable periodic table! Find the atomic weight for beryllium or gallium or any element. An excellent chemistry resource.
What exactly is in your toothpaste?
What about that paper you’re writing on or the bug spray you use in summer?
This site puts science into everyday life, with informative descriptions of the chemistry behind the products we use on a regular basis.
Chemistry Comes Alive: Sample Movies - From the Journal of Chemical Education.
Exciting movies of some explosive, flaming, and colorful chemical reactions. You will need the free QuickTime Player to watch.
ChemMatters - Great online resource for High School chemistry teachers brought to you by the American Chemical Society. Pdf versions of "ChemMatters" magazine, geared towards a high school audience, are available online along with the corresponding teachers’ guides.
A Chemical Jigsaw Puzzle - Learning basic chemistry is even more fun when it's a puzzle! Learn the concept of valency and how to balance equations using this fun visual and tactile method.
Food and Science - Students can learn chemistry through cooking! This site for teachers has lots of fun lesson plans that link chemistry and food preparation.
The Periodic Table of Comic Books - Comics and chemistry together? What could be better? Click on an element in the periodic table and see the comics associated with that element.
The pH Factor - This site will help teachers introduce the concepts of acid and base to middle school students. There are lesson plans, classroom activities, and a teachers guide.
Delights of Chemistry - A trip to this site is sure to spark your interest in chemistry. You can watch videos of exciting chemistry demonstrations, view experiments illustrated with photos and complete with explanations, and browse through a chemical reaction photo gallery.
Chembalancer - This online game with visual aids can help beginning chemistry students learn how to balance chemical equations.
Reactive Reports - Learn about exciting developments in chemistry and related fields by checking out this Web-based chemistry magazine.
Read about the molecule behind a Biblical plague, a marine bacteria that can bubble-wrap iron, and a compound found in a Native American herbal remedy that may hold the key to overcoming antibiotic resistance.
The articles are accessible to a lay audience.
The Learning Matters of Chemistry - Check out the "Computer Graphics" section, which has very cool animations of famous experiments and illustrates important principles of chemistry.
Also, visit the "Interactivy" section for a game of "Periodic TableTris"--a Tetris-like game.Simple, Common, and Interesting Molecules - Ever wonder about the three-dimensional chemical structure of aspirin?
How about caffeine?
Check out this site from the Indiana University Molecular Structure Center.
A Visual Interpretation of the Table of Elements - An innovative and elegant visual tour through the periodic table. Each of the 109 elements is accompanied by a visual image, as well as a description and history (including the origin of its name). These pages are image heavy, and take a while to load.
Multimedia Molecule Extravaganza - Explore animated multimedia movies of DNA and other complex molecules. This is an excellent upper level chemistry resource. Requires QuickTime Player.
Reeko's Mad Scientist Lab - This densely packed site has scads and scads of excellent science and chemistry experiments you can try at home, as well as science book reviews, science tips and more, all delivered in a highly irreverent style.-->
Polymers &
Liquid Crystals - A well- constructed and informative site. Learn basic concepts and check out "downloadable" simulations.
The Macrogalleria - Learn about polymers and polymer science. The site really does take you through a mall (hence the "Macrogalleria") to demonstrate how polymers are used in everyday products.
BioChemNet - (now links to High School Hub. There are still many biology and chemistry links)- An impressive collection of links to biology and chemistry sites.
Chemist's Art Gallery -Animations and visualizations of molecules, polymers, cells, etc. I'm not sure what all the molecules and polymers are, but they sure are pretty!
Chemistry Teaching Resources - The most comprehensive listing of chemistry teaching resources we've come across.
Chemicool Periodic Table - A clickable periodic table that gives in-depth information on each element. The most complete periodic table we've seen on the web to date.
WebElements - A clickable periodic table! Find the atomic weight for beryllium or gallium or any element. An excellent chemistry resource.
Chemical Database
A chemical database is a database specifically designed to store chemical information.
Most chemical databases store information on stable molecules. Chemical structures are traditionally represented using lines indicating chemical bonds between atoms and drawn on paper (2D structural formulae).
While these are ideal visual representations for the chemist, they are unsuitable for computational use and especially for search and storage.
Large chemical databases are expected to handle the storage and searching of information on millions of molecules taking terabytes of physical memory.
Most chemical databases store information on stable molecules. Chemical structures are traditionally represented using lines indicating chemical bonds between atoms and drawn on paper (2D structural formulae).
While these are ideal visual representations for the chemist, they are unsuitable for computational use and especially for search and storage.
Large chemical databases are expected to handle the storage and searching of information on millions of molecules taking terabytes of physical memory.
14.1.07
Demonstration websites for science
http://physics.tas.edu.tw/
http://www.eskimo.com/~billb/scied.html
http://www.exploratorium.edu/publications/Snackbook/Snackbook.html
http://www.eskimo.com/~billb/amateur/ambooks.html
http://www.exploratorium.edu/publications/Hands-On_Science/Snacks
http://www.minnetonka.k12.mn.us/support/science/good.html
http://bluto.uwex.edu/wicip/Ims/science.html
http://www.sfi.fr/est/science.html
http://physics.usc.edu/~gould/ScienceFairs/
http://www.acs.org
http://www.scimedia.com/index.htm
http://www.shef.ac.uk/~chem/web-elements/
http://www.chem.vt.edu/chem-ed/org-home.html
http:///www.ed.gov/technology/plan
http://www.muohio.edu/dragonfly/teacher.htmlx
http://www.teachers.net/lessons/
http://www.enc.org
http://www.tp.umu.se/tiptop
http://www.cpsurf.com/
http://www.physics.purdue.edu/
http://www.aapt.org/
http://physicsweb.org/TIPTOP/
http://www.aip.org/
http://www-hpcc.astro.washington.edu/
http://www.stemnet.nf.ca/~yliu/sciences.html#physics
Vendors:
http://www.arborsci.com
http://www.aimsed.fresno.edu
http://www.edresources.com
http://www.krev.com
http://www.pasco.com
http://www.pitsco.com
http://www.coast.net/simtel/
http://www.fishered.com
http://www.teleport.com/~vernier
http://www.nascofa.com
http://www.ti.com/calc
http://www.sensornet.com
http://www.swpco.com
http://www.sargentwelch.com
http://www.ztek.com
http://www.cyberlearn.com
http://www.eoascientific.com
http://www.casio-usa.com
http://jchemed.chem.wisc.edu
http://www.gene.com/ae
http://ice.chem.wisc.edu/ice
http://www.acculab.com
http://www.ppsisoft.com
http://www.videodiscovery.com/vdyweb
http://www.eskimo.com/~billb/scied.html
http://www.exploratorium.edu/publications/Snackbook/Snackbook.html
http://www.eskimo.com/~billb/amateur/ambooks.html
http://www.exploratorium.edu/publications/Hands-On_Science/Snacks
http://www.minnetonka.k12.mn.us/support/science/good.html
http://bluto.uwex.edu/wicip/Ims/science.html
http://www.sfi.fr/est/science.html
http://physics.usc.edu/~gould/ScienceFairs/
http://www.acs.org
http://www.scimedia.com/index.htm
http://www.shef.ac.uk/~chem/web-elements/
http://www.chem.vt.edu/chem-ed/org-home.html
http:///www.ed.gov/technology/plan
http://www.muohio.edu/dragonfly/teacher.htmlx
http://www.teachers.net/lessons/
http://www.enc.org
http://www.tp.umu.se/tiptop
http://www.cpsurf.com/
http://www.physics.purdue.edu/
http://www.aapt.org/
http://physicsweb.org/TIPTOP/
http://www.aip.org/
http://www-hpcc.astro.washington.edu/
http://www.stemnet.nf.ca/~yliu/sciences.html#physics
Vendors:
http://www.arborsci.com
http://www.aimsed.fresno.edu
http://www.edresources.com
http://www.krev.com
http://www.pasco.com
http://www.pitsco.com
http://www.coast.net/simtel/
http://www.fishered.com
http://www.teleport.com/~vernier
http://www.nascofa.com
http://www.ti.com/calc
http://www.sensornet.com
http://www.swpco.com
http://www.sargentwelch.com
http://www.ztek.com
http://www.cyberlearn.com
http://www.eoascientific.com
http://www.casio-usa.com
http://jchemed.chem.wisc.edu
http://www.gene.com/ae
http://ice.chem.wisc.edu/ice
http://www.acculab.com
http://www.ppsisoft.com
http://www.videodiscovery.com/vdyweb
13.1.07
Chem link Labs
*Acid-Base Titrations
This site has a variety of interactive acid-base titrations that can be performed.
Strong Acid - Strong BaseWeak Acid/Strong BaseStrong Acid/Weak BaseAll CombinationsSketch GraphChoice of Indicators
Gas Laws
This site provides interactivity that covers several gas laws.
Diffusion of gases: Effect of Temperature and Molar MassBoyle's Law ModelRelationship Between Volume, Pressure and Temperature for a Fixed Mass of GasEquilibrium
The equilibrium between H2 + I2 <==> 2 HI. Adjustments can be made so students can to identify how the concentrations vary.
Kinetics
The site has a variety of interactive lab simulations that cover every almost every aspect of kinetics.
Gas KineticsRate expressions: First OrderlRate expressions: Second Order Temperature Effects: Kinetics/Transition State TheoryTemperature Effects: Rate ConstantKinetics & Gas Simulator
Great illustration of the movements of molecules under a variety of conditions.
Le Chatelier's Principle Model
This model demonstrates the attainment of equilibrium in a model chemical reaction. The way in which the position of equilibrium is affected by altering the conditions is summarized by Le Chatelier's principle.
Molecules in Motion
Temperature, mass, the number of particles, and internal pressure can be manipulated to see the effect on the movement of molecules.
Periodicity
These applets provide an excellent look at periodicity of properties amongst the elements.
Periodicity: Atomic & Ionic Radii
Periodicity: Physical Properties
Principle Species & pH in Acid Base Solutions
Pick the volume of a given concentration of an acid and base and it will identify concentrations of each species at the start, before and at equilibrium. Buffers can also be worked with.
Stoichiometry
One of the first numerical problems encountered in introductory chemistry is that of "limiting reagents". The applet does not approach or solve the problem as it would be done with paper and pencil, on the blackboard, or in the textbook. Rather, it serves as a supplement to such calculations, providing imagery that helps students see beyond a route mathematical procedure. In lecture, the instructor may work through the problem on the blackboard, referring to the applet as a constant visual reminder of what is being calculated and why. Outside lecture, students may use the applet while solving problems, to generate and check intermediate results and help them discover and correct their own mistakes.
Variation of Boiling Point with Pressure
Compares the varying pressures and initial temperatures of a water vapor pressure curve, the estimated vapor pressure curve using Trouton's rule, and the methane vapor pressure curve.
This site has a variety of interactive acid-base titrations that can be performed.
Strong Acid - Strong BaseWeak Acid/Strong BaseStrong Acid/Weak BaseAll CombinationsSketch GraphChoice of Indicators
Gas Laws
This site provides interactivity that covers several gas laws.
Diffusion of gases: Effect of Temperature and Molar MassBoyle's Law ModelRelationship Between Volume, Pressure and Temperature for a Fixed Mass of GasEquilibrium
The equilibrium between H2 + I2 <==> 2 HI. Adjustments can be made so students can to identify how the concentrations vary.
Kinetics
The site has a variety of interactive lab simulations that cover every almost every aspect of kinetics.
Gas KineticsRate expressions: First OrderlRate expressions: Second Order Temperature Effects: Kinetics/Transition State TheoryTemperature Effects: Rate ConstantKinetics & Gas Simulator
Great illustration of the movements of molecules under a variety of conditions.
Le Chatelier's Principle Model
This model demonstrates the attainment of equilibrium in a model chemical reaction. The way in which the position of equilibrium is affected by altering the conditions is summarized by Le Chatelier's principle.
Molecules in Motion
Temperature, mass, the number of particles, and internal pressure can be manipulated to see the effect on the movement of molecules.
Periodicity
These applets provide an excellent look at periodicity of properties amongst the elements.
Periodicity: Atomic & Ionic Radii
Periodicity: Physical Properties
Principle Species & pH in Acid Base Solutions
Pick the volume of a given concentration of an acid and base and it will identify concentrations of each species at the start, before and at equilibrium. Buffers can also be worked with.
Stoichiometry
One of the first numerical problems encountered in introductory chemistry is that of "limiting reagents". The applet does not approach or solve the problem as it would be done with paper and pencil, on the blackboard, or in the textbook. Rather, it serves as a supplement to such calculations, providing imagery that helps students see beyond a route mathematical procedure. In lecture, the instructor may work through the problem on the blackboard, referring to the applet as a constant visual reminder of what is being calculated and why. Outside lecture, students may use the applet while solving problems, to generate and check intermediate results and help them discover and correct their own mistakes.
Variation of Boiling Point with Pressure
Compares the varying pressures and initial temperatures of a water vapor pressure curve, the estimated vapor pressure curve using Trouton's rule, and the methane vapor pressure curve.
Chem link Periodic Table
3D Periodic Table of Radii
A depiction of radii of elements and their ions as a Chime.
BK Periodic Table
Each program is an interactive periodic table of the elements. They take full advantage of your computer's capabilities to give you an in-depth look at the elements that make up our earth, the solar system, the galaxy.
Chem Globe
Chemical Elements.com
Create Your Own Model of the Periodic Table
What would it be like to construct that model from scratch? What if you had to group elements by their characteristics and place them on a table close to the other elements in their group, while at the same time logically arranging the atomic weights? What decisions would you make? The stand-alone activity is accompanied by a Teacher's Guide (pdf) with background, lesson procedures, and links to other materials needed for planned instruction. With modification, it is appropriate for grades 5-12.
Elementistory
Environmental Chemistry.com: Periodic Table
Comprehensive data on elements including scores of properties, element names in many languages and most known nuclides is provided by this periodic table.
Eric & Neal's Periodic Table of the Elements
Hyper Chemistry on the Web - The Periodic Table
Interactive Periodic Table of the Elements
Lyrics to the Elements by Tom Lehrer
Mendeleev's Original Periodic Table
NetElements II
NOVA Online Kaboo
Highlighted in the Periodic Table below are some of the important elements that make a firework work. Click on the elements outlined to find out what their contributions are to a firework.
PeriodicTable.com
Three levels of information are provided.
Periodic Table - Cambridge University
Periodic Table - Frontiers in BioScience
Periodic Table - The Irydium Project - Carnegie Mellon
A reference and instruction for scientists of all levels.
Periodic Table - The University of Akron
Periodic Table of Comic Books
Periodic Table of Condiments
Periodic Table of the Elements - Los Alamos Laboratories
Periodic Table of the Elements - MIT
*Periodic Table of Elements - Think Quest
This is THE ULTIMATE SOURCE for virtually every periodic table that exists. Every language imagineable, and an amazing variety of information. Whatever you are looking for, its got be be here.
Periodic Table of Rejected Elements
*Periodic Tables
If the table you are looking for isn't here, with the features you are looking for, in the language of your choice, I'd be amazed. THE most extensive listing of periodic tables anywhere on the web.
Pictoral Periodic Table
The Atomic MAC
The Periodic Table of Poetry
Visual Elements
X-Ray Periodic Table
Web Elements
Web Elements - version 1.2.2
*Web Elements Pro - The University of Sheffield
The most comprehensive periodic table on the Internet.
A depiction of radii of elements and their ions as a Chime.
BK Periodic Table
Each program is an interactive periodic table of the elements. They take full advantage of your computer's capabilities to give you an in-depth look at the elements that make up our earth, the solar system, the galaxy.
Chem Globe
Chemical Elements.com
Create Your Own Model of the Periodic Table
What would it be like to construct that model from scratch? What if you had to group elements by their characteristics and place them on a table close to the other elements in their group, while at the same time logically arranging the atomic weights? What decisions would you make? The stand-alone activity is accompanied by a Teacher's Guide (pdf) with background, lesson procedures, and links to other materials needed for planned instruction. With modification, it is appropriate for grades 5-12.
Elementistory
Environmental Chemistry.com: Periodic Table
Comprehensive data on elements including scores of properties, element names in many languages and most known nuclides is provided by this periodic table.
Eric & Neal's Periodic Table of the Elements
Hyper Chemistry on the Web - The Periodic Table
Interactive Periodic Table of the Elements
Lyrics to the Elements by Tom Lehrer
Mendeleev's Original Periodic Table
NetElements II
NOVA Online Kaboo
Highlighted in the Periodic Table below are some of the important elements that make a firework work. Click on the elements outlined to find out what their contributions are to a firework.
PeriodicTable.com
Three levels of information are provided.
Periodic Table - Cambridge University
Periodic Table - Frontiers in BioScience
Periodic Table - The Irydium Project - Carnegie Mellon
A reference and instruction for scientists of all levels.
Periodic Table - The University of Akron
Periodic Table of Comic Books
Periodic Table of Condiments
Periodic Table of the Elements - Los Alamos Laboratories
Periodic Table of the Elements - MIT
*Periodic Table of Elements - Think Quest
This is THE ULTIMATE SOURCE for virtually every periodic table that exists. Every language imagineable, and an amazing variety of information. Whatever you are looking for, its got be be here.
Periodic Table of Rejected Elements
*Periodic Tables
If the table you are looking for isn't here, with the features you are looking for, in the language of your choice, I'd be amazed. THE most extensive listing of periodic tables anywhere on the web.
Pictoral Periodic Table
The Atomic MAC
The Periodic Table of Poetry
Visual Elements
X-Ray Periodic Table
Web Elements
Web Elements - version 1.2.2
*Web Elements Pro - The University of Sheffield
The most comprehensive periodic table on the Internet.
Chem Link Humor
Buknell Chemistry Songs
All your favorites: How to Make Aspirin Today, Magnesium the Beautiful, Grignard the Beautiful, The Alcohol Substitution March, Off the Alcohol Goes, Ode to an Acetal, Glory, Glory, It's Wolff-Kischner!, Oh, My Ketone, The Aldol Reaction, Synthesis Lament, More Chem Songs
Chem Jokes
A wide variety of chemistry jokes.Chemistry: The Songs of Our Lives
A fantastic collection of semester theme songs.
Dihydrogen Monoxide Research Division
The controversy surrounding dihydrogen monoxide has never been more widely debated, and the goal of this site is to provide an unbiased data clearinghouse and a forum for public discussion. The success of this site depends on you, the citizen concerned about Dihydrogen Monoxide.comments and suggestions.
Good Enough for Chemistry
A tragedy in three scenes.Humor Menu
A range of cartoons and humor.Jokes Related to Chemistry
An attempt at chemical humor.Labrats
LABRATS features the adventures of chemistry major Sid Ford, her neurotic boyfriend Chuck, her somewhat normal roommate Barbara, and dim bass player Marshall.
Song of Cesium
The ancient manuscripts from which these songs are derived are fragmentary, and consequently the accuracy of the following translations must be taken with a grain of Cesium Chloride. In places, the translator has filled in gaps to the best of his ability using available knowledge about the culture and traditions of ancient Cesia much of which, is itself controversial.Swedish Christmas Chemistry
The Swedish Christmas traditions constitute a delightful mixture of originally Pagan rites, derived from the Viking ancestors, and more recently introduced Christian customs.
All your favorites: How to Make Aspirin Today, Magnesium the Beautiful, Grignard the Beautiful, The Alcohol Substitution March, Off the Alcohol Goes, Ode to an Acetal, Glory, Glory, It's Wolff-Kischner!, Oh, My Ketone, The Aldol Reaction, Synthesis Lament, More Chem Songs
Chem Jokes
A wide variety of chemistry jokes.Chemistry: The Songs of Our Lives
A fantastic collection of semester theme songs.
Dihydrogen Monoxide Research Division
The controversy surrounding dihydrogen monoxide has never been more widely debated, and the goal of this site is to provide an unbiased data clearinghouse and a forum for public discussion. The success of this site depends on you, the citizen concerned about Dihydrogen Monoxide.comments and suggestions.
Good Enough for Chemistry
A tragedy in three scenes.Humor Menu
A range of cartoons and humor.Jokes Related to Chemistry
An attempt at chemical humor.Labrats
LABRATS features the adventures of chemistry major Sid Ford, her neurotic boyfriend Chuck, her somewhat normal roommate Barbara, and dim bass player Marshall.
Song of Cesium
The ancient manuscripts from which these songs are derived are fragmentary, and consequently the accuracy of the following translations must be taken with a grain of Cesium Chloride. In places, the translator has filled in gaps to the best of his ability using available knowledge about the culture and traditions of ancient Cesia much of which, is itself controversial.Swedish Christmas Chemistry
The Swedish Christmas traditions constitute a delightful mixture of originally Pagan rites, derived from the Viking ancestors, and more recently introduced Christian customs.
Chem Graphics
Plug-ins to View Graphical Images
QuickTimeRealPlayerShockwave
Windows Media PlayerChimeRasmol3D Molecule
A large collection of 3D chemical structures separated in five different categories, natural, inorganics, pharmaceuticals, biomolecules and various molecules.
3D Virtual Chemistry Library
This molecular database incorporates molecules and information relevant to A-Level studies. In total approximately 150 molecules have been divided into 6 main groups: Simple Molecules, Polymers, Senses, Medical, Horrible Molecules, and Interesting Molecules.
A Fullerene Structure Library
Buckminsterfullerene, C60 long with C70 and a variety of other Buckyballs.
Alphabetic Listing of Chime Molecules
A large collection of Chime molecules, and notes on using Chime.
Animated Molecules
VSEPR models, drawn by Robyn Rindge, rotate molecules using Infini-D. Only the molecules included in General Chemistry by Brady and Humiston 4ed. were rendered. Stills of each animated GIF file are shown.
Atomic Orbitals
The electron orbitals presented represent a volume of space within which an electron would have a certain probability of being based on particular energy states and atoms. The shape of the orbital depends on many factors. The most important are the quantum numbers associated with the particular energy state. These are n, the principal quantum number, l, the oribital quantum number, and m, the angular momentum quantum number. The following table shows some of these shapes.
Atomic Orbitals
The orbitals can be viewed in any order. Using your mouse allows each orbital to rotate. An atomic orbital multiple choice test is also included complete with animation.
CAChe: An Online Molecular Modeling Tutorial
CAChe is an extremely powerful tool used in building molecules.
CAChe - Molecular Modeling Tutorial
CAChe is an extremely powerful tool used in building molecules. This tutorial will guide you through the basics in building molecular structures.
Chem Connections
All molecules shown on this website are part of a smell database, and many are applicable to basic organic studies. To view the real time rotatable images you need a pdb (Protein Data Bank) viewer. An excellent and free pdb viewer available for the PC, MAC and UNIX platforms is Rasmol (currently at version 2.5). For Macintosh users! Here at MultiCHEM, we have developed RasMac v2.5-ucb, a new version of RasMol with many enhancements such as viewing of multiple molecules, distance/angle measurement and more.
Chemistry Art Gallery
Includes organic, inorganic, physical, surface, science, solid state, and structural art.
Chemistry Based Quicktime Movies
These animations, which consist of QuickTime movies, Shockwave Flash Animations, GIF89 Animations, cover usage of various types of equipment for quantitative and qualitative analysis.
Computers in Chemistry at Cabrillo College
Molecular Library 2.0 consists of over 400 molecular models, plus three Java-enhanced viewers, a Chime Tutorial, Chime Student Exercises, a Chime Toolbox, Downloadable C4 Software, Chime Help Center, Molecular Modeling Links, and a Molecular Playground
Crystal Gallery Landscapes of Polarization Microscopy
When oriented molecules such as crystalline chemicals are placed between two polarizing filters, the crystals exhibit amazing colored landscapes or subtle patterns. Shown approximately 10 to 50 times actual size, the chemicals on this page were photographed between "crossed" polarizing filters.
*Crystals
Each crystal image can be maipulated, providing a much clearer understanding of the structures of crystals.Crystal Lattice Structures
Provides an index of common crystal lattice structures. Additional information is available on each structure by clicking on the image.
Icon Bazaar
Select a Class of Compounds fully animated from Amino Acids or CarbohydratesInorganic Structure Database
The structures are viewed (line, ball and stick, space filling and labeled) and measured (bond lengths, bond angles, dihedral angles) with the WebLab Viewer or with either the Chime 2 plugin or RasMol, available for several platforms. The structures are generally arranged alphabetically by the central atom.
Low Molecular Weight Molecules
Provides a look at inorganic crystals and alkanes, branched alkanes, chlorinated alkanes, and cycloalkanes that can be rotated.
MathMol Library
Provides, pdb, VRML images of water, ice, carbon, hydrocarbons.
Molecular Modeling
Provides models for general chemistry and organic chemistry
Molecular Models From Chemistry - Okanagan University College
1400 Molecular Models in .pdb FormatMolecular Visualization Freeware
RasMol-derivative is software for viewing macromolecular structures and their relation to function. Windows or Macintosh computers.Molecules (Javascripts)
A variety of organic molecules which include alkanes, saturated six-membered rings, fused rings, unsaturated rings, aromatic ring, and Fullerenes.
Orbital Types
Provides views of orbitals from the 1s orbital to 3dz2.*Pi Orbital Orbitals of Benzene
Beautifully done images that can be manipulated and pulled through 3 Dimensional space. Fantastic perspectives.
Rolf Clausen's Chemistry Index
Provides information and sites to usage of Chime, VRML, Animated GIFS, Java.
Simple, Common & Interesting Molecules
X-ray Crystallography is one of the principal techniques for studying the structure of molecules and crystals. In the following links, you can examine the structures of a variety of interesting molecules. Whenever possible, the data have been obtained from crystallographic sources, although some of the simple structures are calculated using molecular mechanics techniques.
STM Image Gallery
Organized by IBM, this website takes a look at and through the Scanning Tunneling Microscopy; accompanied by some beautiful photos.
Structures of Inorganic Salts
Animations of elements, halides, and oxides.*
The Molecular Structure Pages
Each of the 409 molecules and ions available on The Molecular Structure Pages can be manipulated to provide a much clearer understanding of molecular structures.
The Structures of Simple Inorganic Solids
This practical is intended to help you understand the manner in which the regular structures of some simple inorganic solids are constructed.
Transition Metal Halides & Oxides
Animations are provided for crystal structures of several common salts with. Excellent representations.
WWU Virtual Molecular Model Kit
A variety of instructional molecules that can be viewed if you have installed either RasMol or Chemscape Chime as a plug-in viewer in your web browser. These molecules can be Interactively sized and rotated. Most of these molecules can be viewed best by using the "Sticks" option under the Display menu.
Visualizing Molecules
Contains Lewis Dot structures, with downloadable files for a variety of molecules.
VRML File Creator - VRML Animation Generator for Chemical Structures
These two go hand-in-hand. Build your chemical and then view it.
VSEPR - University of Sheffield
An excellent source of information that provides about bonding, common geometries, how to predict geometry, examples, isomers, multiple bonds, unpaired electrons, multi-electron pairs and exercises. Several formats of models are presented along with animations.
VSEPR
Provide a table showing examples of the most common geometries encountered using the VSEPR theory. Using RasMol v2.5-ucb, the molecules can be viewed as 3-dimensional structures. Only lone pair electrons on the central atom are shown.
VESPR Table
Provides a comparison of electron pairs and geometries, molecular geometry, examples, and rotatable images.
QuickTimeRealPlayerShockwave
Windows Media PlayerChimeRasmol3D Molecule
A large collection of 3D chemical structures separated in five different categories, natural, inorganics, pharmaceuticals, biomolecules and various molecules.
3D Virtual Chemistry Library
This molecular database incorporates molecules and information relevant to A-Level studies. In total approximately 150 molecules have been divided into 6 main groups: Simple Molecules, Polymers, Senses, Medical, Horrible Molecules, and Interesting Molecules.
A Fullerene Structure Library
Buckminsterfullerene, C60 long with C70 and a variety of other Buckyballs.
Alphabetic Listing of Chime Molecules
A large collection of Chime molecules, and notes on using Chime.
Animated Molecules
VSEPR models, drawn by Robyn Rindge, rotate molecules using Infini-D. Only the molecules included in General Chemistry by Brady and Humiston 4ed. were rendered. Stills of each animated GIF file are shown.
Atomic Orbitals
The electron orbitals presented represent a volume of space within which an electron would have a certain probability of being based on particular energy states and atoms. The shape of the orbital depends on many factors. The most important are the quantum numbers associated with the particular energy state. These are n, the principal quantum number, l, the oribital quantum number, and m, the angular momentum quantum number. The following table shows some of these shapes.
Atomic Orbitals
The orbitals can be viewed in any order. Using your mouse allows each orbital to rotate. An atomic orbital multiple choice test is also included complete with animation.
CAChe: An Online Molecular Modeling Tutorial
CAChe is an extremely powerful tool used in building molecules.
CAChe - Molecular Modeling Tutorial
CAChe is an extremely powerful tool used in building molecules. This tutorial will guide you through the basics in building molecular structures.
Chem Connections
All molecules shown on this website are part of a smell database, and many are applicable to basic organic studies. To view the real time rotatable images you need a pdb (Protein Data Bank) viewer. An excellent and free pdb viewer available for the PC, MAC and UNIX platforms is Rasmol (currently at version 2.5). For Macintosh users! Here at MultiCHEM, we have developed RasMac v2.5-ucb, a new version of RasMol with many enhancements such as viewing of multiple molecules, distance/angle measurement and more.
Chemistry Art Gallery
Includes organic, inorganic, physical, surface, science, solid state, and structural art.
Chemistry Based Quicktime Movies
These animations, which consist of QuickTime movies, Shockwave Flash Animations, GIF89 Animations, cover usage of various types of equipment for quantitative and qualitative analysis.
Computers in Chemistry at Cabrillo College
Molecular Library 2.0 consists of over 400 molecular models, plus three Java-enhanced viewers, a Chime Tutorial, Chime Student Exercises, a Chime Toolbox, Downloadable C4 Software, Chime Help Center, Molecular Modeling Links, and a Molecular Playground
Crystal Gallery Landscapes of Polarization Microscopy
When oriented molecules such as crystalline chemicals are placed between two polarizing filters, the crystals exhibit amazing colored landscapes or subtle patterns. Shown approximately 10 to 50 times actual size, the chemicals on this page were photographed between "crossed" polarizing filters.
*Crystals
Each crystal image can be maipulated, providing a much clearer understanding of the structures of crystals.Crystal Lattice Structures
Provides an index of common crystal lattice structures. Additional information is available on each structure by clicking on the image.
Icon Bazaar
Select a Class of Compounds fully animated from Amino Acids or CarbohydratesInorganic Structure Database
The structures are viewed (line, ball and stick, space filling and labeled) and measured (bond lengths, bond angles, dihedral angles) with the WebLab Viewer or with either the Chime 2 plugin or RasMol, available for several platforms. The structures are generally arranged alphabetically by the central atom.
Low Molecular Weight Molecules
Provides a look at inorganic crystals and alkanes, branched alkanes, chlorinated alkanes, and cycloalkanes that can be rotated.
MathMol Library
Provides, pdb, VRML images of water, ice, carbon, hydrocarbons.
Molecular Modeling
Provides models for general chemistry and organic chemistry
Molecular Models From Chemistry - Okanagan University College
1400 Molecular Models in .pdb FormatMolecular Visualization Freeware
RasMol-derivative is software for viewing macromolecular structures and their relation to function. Windows or Macintosh computers.Molecules (Javascripts)
A variety of organic molecules which include alkanes, saturated six-membered rings, fused rings, unsaturated rings, aromatic ring, and Fullerenes.
Orbital Types
Provides views of orbitals from the 1s orbital to 3dz2.*Pi Orbital Orbitals of Benzene
Beautifully done images that can be manipulated and pulled through 3 Dimensional space. Fantastic perspectives.
Rolf Clausen's Chemistry Index
Provides information and sites to usage of Chime, VRML, Animated GIFS, Java.
Simple, Common & Interesting Molecules
X-ray Crystallography is one of the principal techniques for studying the structure of molecules and crystals. In the following links, you can examine the structures of a variety of interesting molecules. Whenever possible, the data have been obtained from crystallographic sources, although some of the simple structures are calculated using molecular mechanics techniques.
STM Image Gallery
Organized by IBM, this website takes a look at and through the Scanning Tunneling Microscopy; accompanied by some beautiful photos.
Structures of Inorganic Salts
Animations of elements, halides, and oxides.*
The Molecular Structure Pages
Each of the 409 molecules and ions available on The Molecular Structure Pages can be manipulated to provide a much clearer understanding of molecular structures.
The Structures of Simple Inorganic Solids
This practical is intended to help you understand the manner in which the regular structures of some simple inorganic solids are constructed.
Transition Metal Halides & Oxides
Animations are provided for crystal structures of several common salts with. Excellent representations.
WWU Virtual Molecular Model Kit
A variety of instructional molecules that can be viewed if you have installed either RasMol or Chemscape Chime as a plug-in viewer in your web browser. These molecules can be Interactively sized and rotated. Most of these molecules can be viewed best by using the "Sticks" option under the Display menu.
Visualizing Molecules
Contains Lewis Dot structures, with downloadable files for a variety of molecules.
VRML File Creator - VRML Animation Generator for Chemical Structures
These two go hand-in-hand. Build your chemical and then view it.
VSEPR - University of Sheffield
An excellent source of information that provides about bonding, common geometries, how to predict geometry, examples, isomers, multiple bonds, unpaired electrons, multi-electron pairs and exercises. Several formats of models are presented along with animations.
VSEPR
Provide a table showing examples of the most common geometries encountered using the VSEPR theory. Using RasMol v2.5-ucb, the molecules can be viewed as 3-dimensional structures. Only lone pair electrons on the central atom are shown.
VESPR Table
Provides a comparison of electron pairs and geometries, molecular geometry, examples, and rotatable images.
Subscribe to:
Posts (Atom)