Silicon
Silicon (Si) is a metalloid with atomic number 14 and an atomic mass of 28.085. Its electron configuration is [Ne] 3s2 3p2, which gives it 4 valence electrons.
Silicon key data
| Symbol | Si |
|---|---|
| Atomic number | 14 |
| Atomic mass (standard atomic weight) | 28.085 |
| Molar mass | 28.085 g/mol |
| Protons | 14 |
| Neutrons (most abundant isotope, silicon-28) | 14 |
| Electrons (neutral atom) | 14 |
| Valence electrons | 4 |
| Category | Metalloid |
| Period | 3 |
| Group | 14 |
| Block | p-block |
| Noble gas notation | [Ne] 3s2 3p2 |
| Full electron configuration | 1s2 2s2 2p6 3s2 3p2 |
| Electrons per shell | 2, 8, 4 |
Atomic mass: IUPAC CIAAW abridged standard atomic weights, 2024. Most abundant isotope: NIST Atomic Weights and Isotopic Compositions.
The values are facts and free to use; this page’s selection and presentation are © 2026 ScienceQuest.
Measured properties of silicon
From PubChem, the US National Institutes of Health. Public domain. The discovery year is the year silicon was first isolated, from Wikipedia’s timeline of chemical element discoveries, in place of PubChem’s 1854.
| Melting point | 1687 K (1413.9 °C), 33rd of 103 by melting point |
|---|---|
| Boiling point | 3538 K (3264.9 °C), 27th of 93 by boiling point |
| Density | 2.33 g/cm³, 74th of 96 by density |
| State at room temperature | Solid |
| Electronegativity | 1.9 (Pauling), joint 36th of 95 by electronegativity |
| Van der Waals radius | 210 pm, joint 46th of 99 by atomic radius |
| First ionisation energy | 8.152 eV (786.5 kJ/mol), 33rd of 102 by first ionisation energy |
| Electron affinity | 1.385 eV (133.6 kJ/mol), 14th of 57 by electron affinity |
| Common oxidation states | +4, +2, −4 |
| Discovered | 1823 |
Each rank counts down from the highest value, among the elements PubChem’s table gives one for, and links to that property ranked across the whole table. All of them are collected under periodic trends.
Silicon electron configuration
The full electron configuration of silicon is 1s2 2s2 2p6 3s2 3p2. With the noble-gas core collapsed it is [Ne] 3s2 3p2, and the outermost subshell is 3p2.
Why group and block follow from this is set out in how the periodic table maps electron configuration, and the electron configuration of every element is listed on one page.
Mass of one silicon atom
A molar mass is grams per mole, so dividing by the Avogadro constant gives the mass of a single atom, or for an element with more than one natural isotope the average mass of its atoms, and the reciprocal gives how many atoms sit in a gram.
Mass of one atom
- one atom = 28.085 / (6.02214076 × 10²³)
- = 4.6636 × 10⁻²³ g
Atoms in one gram
- atoms per gram = 6.02214076 × 10²³ / 28.085
- = 2.1443 × 10²² atoms
Silicon on the periodic table
Silicon is in period 3, group 14, in the p-block.
The other elements of group 14 are carbon, germanium, tin, lead and flerovium.