Electron configurations are a list of the subshells on an atom that are occupied.
Each subshell has a shell number and a letter designation (1s for example).
The number of electrons is given by a superscript. For H the electron configuration is 1s1.
As
maximum number of electrons per subshell (
s subshell - 2,
p subshell - 6,
d subshell - 10) corresponds to the number of groups in the blocks in the periodic table, the periodic table can be used as a guide for constructing the electron configuration of an element.
| | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 |
| 1 | | | | | |
| 2 | | | | | | | | |
| 3 | | | | | | | | |
| 4 | | | | | | | | | | | | | | | | | | |
| 4 | | | | | | | | | | | | | | | | | | |
| 4 | | | | | | | | | | | | | | | | | | |
s-block
2 groups | ———d-block————
10 groups | ——p-block——
6 groups |