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Supplier Data - Silicon (Si) (Goodfellow)

Silicon (Si) was discovered in 1824 by J.J. Berzelius in Stockholm, Sweden.

Abundance and Occurrence

After carbon, Silicon is the most abundant element on earth, the abundance being 277,000 ppm. Silicon is generally present as a silicate, these being found in many rocks, clays and soils.

Extraction

Silicon is obtained by reducing silica (sand, SiO2), with carbon. Further purification of the element for applications requiring high purity material (e.g. semi conductor devices) is achieved by zone refining, the resulting purity being better than 1:109. Silicon exists in two allotropic forms; brown Silicon is a powder, whereas crystalline (metallic) Silicon is grey and it is the latter which is more widely used. Bulk Silicon is unreactive towards oxygen, water, acids (excluding HF), but is soluble in hot alkalis.

Applications

Silicon has many applications in various industries; for example, ultra high purity Silicon is used in the semiconductor industry as a result of its semiconducting properties. Silicon is also used as an alloying element in the manufacture of certain alloys (e.g. ferrosilicon, an alloy of iron and silicon which is used to introduce Silicon into steel and cast iron). It is also used in the manufacture of glass.

Silicon can also be used in the manufacture of glass – Image Credit – Havoc/Shutterstock

Silicon can also be used in the manufacture of glass – Image Credit – Havoc/Shutterstock

Key Properties

The key properties of Silicon are tabulated below.

Table 1. Key properties

Atomic Properties
Atomic number 14
Atomic radius - Goldschmidt ( nm ) 0.117
Atomic weight ( amu ) 28.0855
Crystal structure Diamond
Electronic structure Ne 3s2 3p2
Photo-electric work function ( eV ) 4.2
Thermal neutron absorption cross-section ( Barns ) 0.16
Valences shown 4
Ionisation Potential No. eV
1 8.15
2 16.3
3 33.5
4 45.1
5 167
6 205
Natural Isotope Distribution Mass No. %
28 92.23
29 4.67
30 3.10
Electrical Properties
Electrical resistivity @ 20 °C ( µOhm.cm ) 23 x 1010
Thermal emf against Pt (cold 0 °C - hot 100 °C) ( mV ) -41.56
Mechanical Properties
Material condition Polycrystalline
Bulk modulus ( GPa ) 100
Hardness - Mohs 7.0
Poisson’s ratio 0.42
Tensile modulus ( GPa ) 113
Physical Properties
Boiling point (°C ) 2355
Density @ 20 °C ( g.cm-3 ) 2.34
Melting point (°C ) 1410
Thermal Properties
Coefficient of thermal expansion @ 0-100 °C ( x10-6 K-1 ) 4.7-7.6
Latent heat of evaporation ( J.g-1 ) 13700
Latent heat of fusion ( J.g-1 ) 1650
Specific heat @ 25 °C ( J.K-1.kg-1 ) 703
Thermal conductivity @ 0-100 °C ( W m-1 K-1 ) 80-150

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