Periodic Table


Atomic number: 14
Atomic weight: 28.0855
Symbol: Si
Group number: 14
Electronic configuration: [Ne].3s2.3p2


Silicon is present in the sun and stars and is a principal component of a class of meteorites known as aerolites. Silicon makes up 25.7% of the earth's crust by weight, and is the second most abundant element, exceeded only by oxygen. It is found largely as silicon oxides such as sand (silica), quartz, rock crystal, amethyst, agate, flint, jasper and opal. Silicon is found also in minerals such as asbestos, feldspar, clay and mica.

Silicon is important in plant and animal life. Diatoms in both fresh and salt water extract silica from the water to use as a component of their cell walls. Silicon is an important ingredient in steel. Silicon carbide is one of the most important abrasives. Workers in environments where silicaceous dust is breathed may develop a serious lung disease known as silicosis.

Hydrolysis and condensation of substituted chlorosilanes can be used to produce a very great number of polymeric products, or silicones. These range from liquids to hard, glasslike solids with many useful properties.

Elemental silicon transmits more than 95% of all wavelengths of infrared and and has been used in lasers to produce coherent light at 456 nm.

General information

Discoveror: Jöaut;ns Jacob Berzelius
Date discovered: 1824
Discovered at: Sweden
Meaning of name: From the Latin word "silicis" meaning "flint"

Physical data

Standard state: solid at 298 K
Colour: dark grey with a bluish tinge
Density of solid at ambient temperature/kg m-3: 2330
Molar volume/cm3: 12.06

Radii /pm

Atomic: 111
Covalent (single bond):
Pauling radius for the ion [Si]-: 384

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius95.1115.1no datano data


Both values are quoted on the Pauling scale.

Pauling: 1.90
Allred Rochow: 1.74

Crystal Structure

structure: diamond

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.


Temperatures (/K)

melting point: 1687
boiling point: 3173

Enthalpies /kJ mol-1

fusion: 50.2
vaporization: 359

single bond enthalpies:
Si-F Si-Cl Si-Br Si-I Si-Si
565 381 310 234 326.8

Ionization enthalpies /kJ mol-1

Number Enthalpy


This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
28Si27.9769271 (7)92.23 (1)
29Si28.9764949 (7)4.67 (1)
30Si29.9737707 (7)3.10 (1)

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/Si.html