What is the atomic number of silicon?

Silicon has atomic number 14, meaning its nucleus contains exactly 14 protons. It is the 14th element on the periodic table, located in Period 3, Group 14 (carbon group), below carbon and above germanium.

What is the electron configuration of silicon?

Silicon has the electron configuration 1s² 2s² 2p⁶ 3s² 3p², often written as [Ne] 3s² 3p² in noble gas notation. It has four valence electrons, which gives silicon its tetrahedral bonding geometry in most compounds and in its crystal lattice.

How many stable isotopes does silicon have?

Silicon has three stable isotopes: Silicon-28 (92.223% natural abundance), Silicon-29 (4.685%), and Silicon-30 (3.092%). Silicon-29 is the only stable silicon isotope with a nonzero nuclear spin (I = 1/2), making it useful in NMR spectroscopy.

Is silicon a metal, nonmetal, or metalloid?

Silicon is classified as a metalloid (also called a semimetal). It has a lustrous metallic appearance but conducts electricity only under certain conditions, which is the basis of its semiconductor behavior. Its conductivity lies between that of metals and insulators.

Why is silicon so important in electronics?

Silicon has a band gap of 1.12 eV at room temperature, which is ideal for transistors and diodes. It can be doped with small amounts of boron (p-type) or phosphorus (n-type) to control conductivity precisely. Combined with abundant supply and mature oxide passivation (SiO₂), it became the foundation of the integrated circuit industry.

What is the most common silicon compound?

Silicon dioxide (SiO₂), also known as silica, is the most common silicon compound. It makes up roughly 59% of Earth's crust by mass (counting all silicate minerals). Quartz, sand, flint, and many gemstones are forms of SiO₂. It is also used as the gate insulator in MOSFET transistors.

What is the standard atomic weight of silicon?

The standard atomic weight of silicon is 28.085 u (IUPAC 2021), reflecting the weighted average of its three naturally occurring isotopes.

Silicon Element Properties

Complete reference for Silicon (Si, element 14): atomic data, electron configuration, isotopes, physical constants, and chemical behavior.

14 Si 28.085

Silicon

Metalloid — Period 3, Group 14

Atomic Identity

Atomic Number

Symbol

Standard Atomic Wt.

28.085 u

IUPAC 2021

Period

Group

IVA

Block

p-block

CAS Number

7440-21-3

Discovery

Jöns J. Berzelius

1823

Named By

Berzelius

Latin: silicis

Electron Configuration

Full notation 1s² 2s² 2p⁶ 3s² 3p²

Noble gas shorthand [Ne] 3s² 3p²

Electrons per shell 2, 8, 4

Valence electrons 4

Unpaired electrons 2

Spin multiplicity 3 (triplet)

Orbital Diagram (3p)

2 unpaired electrons in 3p (Hund's rule)

Paramagnetic

2 unpaired electrons

Isotopes of Silicon

Isotope	Symbol	Protons	Neutrons	Mass (u)	Natural Abundance	Stability
Silicon-28	²⁸Si	14	14	27.9769265325	92.223%	Stable
Silicon-29	²⁹Si	14	15	28.9764946649	4.685%	Stable
Silicon-30	³⁰Si	14	16	29.973770136	3.092%	Stable
Silicon-32	³²Si	14	18	31.97415154	Trace	Unstable Radioactive — β⁻, t½ = 153 yr

Physical Properties

State at STP Solid

Appearance Blue-grey lustrous solid

Crystal Structure Diamond cubic

Density 2.329 g/cm³ (at 25 °C)

Melting Point 1414 °C (1687 K)

Boiling Point 3265 °C (3538 K)

Heat of Fusion 50.21 kJ/mol

Heat of Vaporization 383 kJ/mol

Specific Heat Capacity 19.789 J/(mol·K)

Thermal Conductivity 149 W/(m·K)

Electrical Resistivity 2.3×10³ Ω·m (intrinsic)

Mohs Hardness 6.5

Chemical Properties

Electronegativity (Pauling) 1.90

Electron Affinity 134.068 kJ/mol

1st Ionization Energy 786.5 kJ/mol

2nd Ionization Energy 1577.1 kJ/mol

3rd Ionization Energy 3231.6 kJ/mol

4th Ionization Energy 4355.5 kJ/mol

Covalent Radius 111 pm

Van der Waals Radius 210 pm

Oxidation States +4, +2, −4

Band Gap (300 K) 1.12 eV

Electron Mobility ~1400 cm²/(V·s)

Hole Mobility ~450 cm²/(V·s)

Ground State Quantum Numbers

Principal (n) 3 (valence shell)

Azimuthal (l) 1 (p orbital, valence)

Magnetic (mℓ) 0, +1 (two half-filled)

Spin (m‑) +½ each (Hund's rule)

Term symbol ³P₀

Ground state config [Ne] 3s² 3p²

Abundance & Nuclear Data

Earth's crust (mass) 27.7% (2nd most abundant)

Universe (mass fraction) 6.5×10⁻⁴

Ocean (mg/L) ~2.2 mg/L

Human body (ppm) ~18 ppm (by mass)

Nuclear spin (²⁹Si) I = ½

NMR frequency (²⁹Si) 79.50 MHz at 9.4 T

Key Facts About Silicon

Second Most Abundant Element

Silicon makes up about 27.7% of Earth's crust by mass, making it the second most abundant element after oxygen.

Semiconductor Foundation

Silicon's 1.12 eV band gap and excellent oxide formation (SiO₂) make it the cornerstone of modern microelectronics and computing.

Solar Energy

Crystalline silicon accounts for over 90% of all solar photovoltaic panels installed worldwide, converting sunlight directly into electricity.

Silicate Minerals

Silicon dioxide (SiO₂) and silicate minerals form the bulk of Earth's crust. Quartz, feldspar, mica, and clay minerals are all silicates.

High Melting Point

Silicon melts at 1414 °C, much higher than most metals, which enables its use in high-temperature applications and as a refractory material.

Silicon Carbide

SiC (carborundum) is nearly as hard as diamond (Mohs 9.5) and is used as an abrasive, in high-power electronics, and in electric vehicle inverters.

Copied to clipboard

Summary

Silicon is the second most abundant element in Earth's crust after oxygen, with atomic number 14 and symbol Si. A lustrous blue-grey metalloid, it sits in Period 3, Group 14 of the periodic table. Silicon's semiconductor properties underpin virtually all modern electronics, from computer processors to solar cells. This reference compiles the essential physical constants, quantum numbers, isotope data, electron configuration, and chemical properties of silicon in one place.

How it works

Browse the atomic identity section for symbol, atomic number, and standard atomic weight.
Check the electron configuration panel for orbital notation and quantum numbers.
Review the isotopes table for stable silicon isotopes including natural abundances.
Consult the physical properties panel for melting point, boiling point, density, and state at STP.
Use the chemical properties section to understand reactivity, oxidation states, and electronegativity.
Copy any value with one click for use in reports or calculations.

Use cases

Look up silicon constants for chemistry or materials science homework.
Verify atomic data when writing lab reports or research papers.
Reference isotope masses for nuclear chemistry or geochronology.
Check thermodynamic constants for semiconductor or solar energy engineering.
Teach or learn metalloid properties using silicon as the defining example.
Confirm electron configuration before writing molecular orbital or Lewis dot diagrams.
Research silicon compounds for electronics, photovoltaics, or nanotechnology work.
Quick-reference band gap, ionization energy, and electronegativity for materials analysis.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu