Silicon has 14 electrons arranged as 2, 8, 4 across 3 shells, which is why it sits in period 3.
Electrons fill orbitals in order of increasing energy: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p… Each s orbital holds 2 electrons, p holds 6 and d holds 10. Placing Silicon's 14 electrons in that order gives 1s2 2s2 2p6 3s2 3p2.
| Atomic number | 14 |
| Symbol | Si |
| Atomic mass | 28.085 u |
| Group | 14 |
| Period | 3 |
| Block | p-block |
| Category | Metalloid |
| Valence electrons | 4 |
| Element | Configuration |
|---|---|
| Carbon | [He] 2s2 2p2 |
| Germanium | [Ar] 3d10 4s2 4p2 |
| Tin | [Kr] 4d10 5s2 5p2 |
| Lead | [Xe] 4f14 5d10 6s2 6p2 |
| Flerovium | [Rn] 5f14 6d10 7s2 7p2 |
Elements in the same group have the same number of outer electrons, which is why they behave alike.