MetalloidElement 14 · p-block

Silicon (Si)

Silicon (Si) is a metalloid with atomic number 14 and a standard atomic weight of 28.085. At room temperature it is a solid that melts at 1,414 °C and boils at 3,265 °C.

14SiSilicon28.085

Atomic number

protons

Atomic weight

28.085

CIAAW 2024

Melting point

1,414 °C

1,687.15 K

Boiling point

3,265 °C

3,538.15 K

Density

2.33 g/cm³

near room temperature

Electronegativity

1.9

Pauling scale

State at 25 °C

Solid

Discovered

1824

Sweden

Silicon at a glance

Identity

Symbol	Si
Atomic number (Z)	14
Atomic weight	28.085 ± 0.001 (CIAAW 2024)
Category	Metalloid
Group	14 — carbon group
Period	3
Block	p-block
CAS number	7440-21-3

Atomic properties

Electron configuration	[Ne] 3s² 3p² Full: 1s² 2s² 2p⁶ 3s² 3p²
Electrons per shell	2, 8, 4
Oxidation states	-4, +4 Less common: -3, -2, -1, 0, +1, +2, +3
Electronegativity (Pauling)	1.9
First ionisation energy	8.152 eV (786.5 kJ/mol) 2nd: 16.346 eV · 3rd: 33.493 eV
Electron affinity	1.389 eV
Atomic radius (empirical)	110 pm
Covalent radius	116 pm
Van der Waals radius	210 pm

Physical properties

State at 25 °C	Solid
Melting point	1,414 °C · 2,577.2 °F · 1,687.15 K
Boiling point	3,265 °C · 5,909 °F · 3,538.15 K
Density	2.3296 g/cm³
Specific heat capacity	0.712 J/(g·K)
Thermal conductivity	149 W/(m·K)
Crystal structure	Diamond cubic

Isotopes & abundance

Natural occurrence	Primordial
Radioactive	No
Natural isotopes (abundance)	²⁸Si 92.2545%, ²⁹Si 4.672%, ³⁰Si 3.0735%
Stable isotopes	3
Known isotopes	24
Abundance in Earth's crust	282,000 mg/kg
Abundance in seawater	2.2 mg/L

Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.

Silicon electron configuration

Silicon has 14 electrons. Written in short form, its ground-state configuration is [Ne] 3s² 3p² — the electrons of the noble gas neon, plus 3s² 3p².Written out in full: 1s² 2s² 2p⁶ 3s² 3p².

As a member of group 14 it has 4 valence electrons in its outer shell (shell 3), which largely decide its chemistry.

3s↑↓

3p↑↑

Discovery and name

Discovered

1824 — Jöns Jacob Berzelius · Sweden.

Name

Latin silex/silicis, flint.

Known for

The second most abundant element in the crust (after oxygen). Ultra-pure silicon is the material of computer chips and most solar cells; silica makes glass and concrete.

Isotopes of silicon

Naturally occurring silicon is a mix of 3 isotopes. Each has 14 protons; they differ in the number of neutrons:

Isotope	Protons	Neutrons	Natural abundance	Stability
²⁸Si	14	14	92.2545%	stable
²⁹Si	14	15	4.672%	stable
³⁰Si	14	16	3.0735%	stable

24 isotopes of silicon are known in our data set (half-lives as published in nuclear data tables).

Silicon compared with group 14

The other elements in group 14 (carbon group), from top to bottom of the table:

Element	Z	Atomic weight	Melting point	Boiling point	Density	Electronegativity
Carbon	6	12.011	—	3,642 °C	2.2 g/cm³	2.55
Silicon	14	28.085	1,414 °C	3,265 °C	2.33 g/cm³	1.9
Germanium	32	72.630	938 °C	2,833 °C	5.323 g/cm³	2.01
Tin	50	118.71	232 °C	2,586 °C	7.287 g/cm³	1.96
Lead	82	207.2	327 °C	1,749 °C	11.3 g/cm³	2.33
Flerovium	114	[290]	—	—	9.928 g/cm³ (pred.)	—

Frequently asked questions

6 answers

What is the atomic mass of silicon?

The standard atomic weight of silicon is 28.085 ± 0.001 (CIAAW 2024), so one mole weighs about 28.085 grams.

How many protons, neutrons and electrons does silicon have?

A neutral silicon atom has 14 protons and 14 electrons. Its most common isotope, silicon-28, has 14 neutrons.

What is the electron configuration of silicon?

[Ne] 3s² 3p² (in full: 1s² 2s² 2p⁶ 3s² 3p²).

What are the melting and boiling points of silicon?

Silicon melts at 1,414 °C (2,577.2 °F) and boils at 3,265 °C (5,909 °F).

Is silicon a metal?

Silicon is a metalloid — it has properties between metals and nonmetals. It is in group 14, period 3, and is a solid at room temperature.

Who discovered silicon?

1824 — Jöns Jacob Berzelius (Sweden).