Element: Silicon
General data
| Element name | Silicon |
|---|---|
| Chemical symbol | Si |
| Atomic number Z | 14 |
| Year discovered | 1854 |
| Standard state (25°C) | Solid |
| Category | Metalloid |
| Block | p |
| Atomic mass | 28.085 |
| CPK color | #F0C8A0 |
Physical properties
| Melting point | 1687 K (1414 °C) |
|---|---|
| Boiling point | 3538 K (3265 °C) |
| Density | 2.3296 g/cm³ |
Energy properties
| First ionization energy | 8.152 eV |
|---|---|
| Electron affinity | 1.385 eV |
Atomic structure
| Protons | 14 (Atomic number) |
|---|---|
| Neutrons (Si-28, most abundant isotope) | 14 |
| Electrons | 14 |
| Electron configuration | [Ne] 3s² 3p² |
| Oxidation states | +4, +2, -4 |
| Electronegativity (Pauling) | 1.9 |
| Atomic radius (van der Waals) | 210 pm |
Ionization energies - NIST ASD (14 states)
| State | Charge | Ioniz. energy (eV) | Type |
|---|---|---|---|
| Si I | 0+ | 8.15168 ± 0.00003 | measured |
| Si II | 1+ | 16.34585 ± 0.00004 | measured |
| Si III | 2+ | 33.493 ± 0.00009 | measured |
| Si IV | 3+ | 45.14179 ± 0.00007 | measured |
| Si V | 4+ | 166.767 ± 0.003 | measured |
| Si VI | 5+ | 205.279 ± 0.005 | semi-empirical |
| Si VII | 6+ | 246.57 ± 0.05 | semi-empirical |
| Si VIII | 7+ | 303.59 ± 0.05 | semi-empirical |
| Si IX | 8+ | 351.28 ± 0.06 | semi-empirical |
| Si X | 9+ | 401.38 ± 0.04 | semi-empirical |
| Si XI | 10+ | 476.273 ± 0.019 | semi-empirical |
| Si XII | 11+ | 523.415 ± 0.007 | calculated |
| Si XIII | 12+ | 2437.65805 ± 0.00017 | calculated |
| Si XIV | 13+ | 2673.177958 ± 0.000017 | calculated |
Value type as given by NIST ASD: measured - from evaluated experimental data; calculated - from ab initio calculations (mostly highly ionised atoms that have not been measured; for the simplest ones, e.g. H I, the calculation is more accurate than measurement); semi-empirical - from interpolation, extrapolation or another semi-empirical method.
Photos
no data
Isotopes (23)
| A | N | Half-life | Decay |
|---|---|---|---|
| Si-22 | 8 | 28.4 ms | EC/β⁺ |
| Si-23 | 9 | 47 ms | EC/β⁺ |
| Si-24 | 10 | 141.4 ms | EC/β⁺ |
| Si-25 | 11 | 219.2 ms | EC/β⁺ |
| Si-26 | 12 | 2.2452 s | EC/β⁺ |
| Si-27 | 13 | 4.111 s | EC/β⁺ |
| Si-28 | 14 | stable | - |
| Si-29 | 15 | stable | - |
| Si-30 | 16 | stable | - |
| Si-31 | 17 | 157.24 min | β⁻ |
| Si-32 | 18 | 163 a | β⁻ |
| Si-33 | 19 | 6.17 s | β⁻ |
| Si-34 | 20 | 2.77 s | β⁻ |
| Si-35 | 21 | 0.78 s | β⁻ |
| Si-36 | 22 | 503 ms | β⁻ |
| Si-37 | 23 | 141 ms | β⁻ |
| Si-38 | 24 | 63 ms | β⁻ |
| Si-39 | 25 | 38.7 ms | β⁻ |
| Si-40 | 26 | 30 ms | β⁻ |
| Si-41 | 27 | 20 ms | β⁻ |
| Si-42 | 28 | 15.0 ms | β⁻ |
| Si-43 | 29 | 13 ms | β⁻ |
| Si-44 | 30 | unknown | β⁻ |
Data sources
- PubChem Periodic Table API - Retrieved on 29 June 2026 - licence: CC0
- IUPAC CIAAW - Abridged Standard Atomic Weights 2024 - Table version: 2024 - licence: Public domain
- NNDC Wallet Cards 2023 - Data as of 15 October 2024 - licence: Public domain
- NIST Atomic Spectra Database (ASD) - Retrieved on 29 June 2026 - licence: © U.S. Secretary of Commerce