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Representative Elements
| Remember from the earlier review of electron configurations that H, Li and
Na all ended with s1. If you look at the rest of the elements in that group you
will see that the similarity continues on down the periodic table. All of the elements in
group Ia end in s1 for their electron configuration. What is different about
them is which level of s1 they end with. Notice also that this periodic table
only shows the last part of the electron configuration. The reason for this is that the
chemical properties of an element are determined by the outermost
electron structure.
So this periodic table was prepared with just those outermost electron configurations
written on it. |
| Ia |
| H 1s1 |
| Li 2s1 |
| Na 3s1 |
| K 4s1 |
| Rb 5s1 |
| Cs 6s1 |
| Fr 7s1 |
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| Now look at group IIa, all of them end in s2 but a different s2
for each one: 2s2 for beryllium, 3s2 for magnesium, and so on. Next,
what comes after the s sublevel is filled? If we go one electron past magnesium, we get
aluminum. Its outermost electron configuration is 3s23p1. Notice
that if you look above and below aluminum, all of the outermost electron configurations
for this group of elements have the same pattern. What is different is which period they
are in. Boron is 2s22p1. Aluminum is 3s23p1.
Gallium is Ga and is an element you didn't have to memorize, but from its position on the
periodic table, you can see that it is 4s24p1. And so on, on down. |
| IIa |
IIIa |
| Be 2s2 |
B 2s22p1 |
| Mg 3s2 |
Al 3s23p1 |
| Ca 4s2 |
Ga 4s24p1 |
| Sr 5s2 |
In 5s25p1 |
| Ba 6s2 |
Tl 6s26p1 |
| Ra 7s2 |
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| If you keep going to the right on the periodic table, notice how with each
column there is one more p electron in each of the energy levels, right over to the inert
gases. |
B
2s22p1 |
C
2s22p2 |
N
2s22p3 |
O
2s22p4 |
F
2s22p5 |
Ne
2s22p6 |
Al
3s23p1 |
Si
3s23p2 |
P
3s23p3 |
S
3s23p4 |
Cl
3s23p5 |
Ar
3s23p6 |
Ga
4s24p1 |
Ge
4s24p2 |
As
4s24p3 |
Se
4s24p4 |
Br
4s24p5 |
Kr
4s24p6 |
In
5s25p1 |
Sn
5s25p2 |
Sb
5s25p3 |
Te
5s25p4 |
I
5s25p5 |
Xe
5s25p6 |
Tl
6s26p1 |
Pb
6s26p2 |
Bi
6s26p3 |
Po
6s26p4 |
At
6s26p5 |
Rn
6s26p6 |
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