|
 |
|
Note:
Promethium (Pm) does not occur naturally in
the Earth's crust. It is a radio active
element that has only been made
artificially as a product of uranium
fission. |
Electronic
Structure of the Atoms
| |
1st shell |
2nd Shell |
3rd Shell |
4th Shell |
5th Shell |
6th shell |
| La |
2 |
8 |
18 |
18 |
9 |
2 |
| Ce |
2 |
8 |
18 |
20 |
8 |
2 |
| Pr |
2 |
8 |
18 |
21 |
8 |
2 |
| Nd |
2 |
8 |
18 |
22 |
8 |
2 |
| Pm |
2 |
8 |
18 |
23 |
8 |
2 |
| Sm |
2 |
8 |
18 |
24 |
8 |
2 |
| Eu |
2 |
8 |
18 |
25 |
8 |
2 |
| Gd |
2 |
8 |
18 |
25 |
9 |
2 |
| Tb |
2 |
8 |
18 |
27 |
8 |
2 |
| Dy |
2 |
8 |
18 |
28 |
8 |
2 |
| Ho |
2 |
8 |
18 |
29 |
8 |
2 |
| Er |
2 |
8 |
18 |
30 |
8 |
2 |
| Tm |
2 |
8 |
18 |
31 |
8 |
2 |
| Yb |
2 |
8 |
18 |
32 |
8 |
2 |
| Lu |
2 |
8 |
18 |
32 |
9 |
2 |
It becomes clear (from the
information shown in the table) why the
properties of these elements are so similar. In
most cases, the fifth shell (energy level) and
the sixth shell each contain the same number of
electrons.
The lanthanides are further
divided into the "light" lanthanides (Lanthanum
to Samarium) and the "heavy" lanthanides
(Europium to Lutetium). The "light" lanthanides
are more abundant in the Earth's crust than the
"heavy" lanthanides (although even the least
abundant lanthanide is more common than silver!)
All lanthanides are
considered as Group 3 elements because they form
3+ ions. |
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