Electronic configuration refers to the arrangement of electrons in the different energy levels or shells of an atom.
It can be calculated by the formula: 2n 2
For insatnace : by the above formula we can calculate the total number of electrons in 2nd shell;
n=2
2(2)2=8 electrons
Let’s have a look at the electronic configuration of the first 18 elements:
| Element | Symbol | Atomic Number | Electronic Configuration |
|---|---|---|---|
| Hydrogen | H | 1 | 1s1 |
| Helium | He | 2 | 1s2 |
| Lithium | Li | 3 | 1s2 2s1 |
| Beryllium | Be | 4 | 1s2 2s2 |
| Boron | B | 5 | 1s2 2s2 2p1 |
| Carbon | C | 6 | 1s2 2s2 2p2 |
| Nitrogen | N | 7 | 1s2 2s2 2p3 |
| Oxygen | O | 8 | 1s2 2s2 2p4 |
| Fluorine | F | 9 | 1s2 2s2 2p5 |
| Neon | Ne | 10 | 1s2 2s2 2p6 |
| Sodium | Na | 11 | 1s2 2s2 2p6 3s1 |
| Magnesium | Mg | 12 | 1s2 2s2 2p6 3s2 |
| Aluminum | Al | 13 | 1s2 2s2 2p6 3s2 3p1 |
| Silicon | Si | 14 | 1s2 2s2 2p6 3s2 3p2 |
| Phosphorus | P | 15 | 1s2 2s2 2p6 3s2 3p3 |
| Sulfur | S | 16 | 1s2 2s2 2p6 3s2 3p4 |
| Chlorine | Cl | 17 | 1s2 2s2 2p6 3s2 3p5 |
| Argon | Ar | 18 | 1s2 2s2 2p6 3s2 3p6 |