Silicon
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Silicon is a metalloid element belonging to the Group IV of the periodic table. It is represented by Si. Silicon is the second most abundant element in the earth’s crust (25.7% by weight). In nature silicon exists in various forms of silicon (IV) oxide in sand quartz and flint, and as silicate minerals in igneous rocks. It belongs to the group IVA and 3rd group. Silicon is characterised by
PROPERTIES
- Atomic number 14
- Relative atomic mass 28.086
- Relative density 2.33
- Melting point 1410OC
- Boiling point 2355OC ( the Boiling and melting points of Si are notably high owing to their tendencies of C and Si to form giant molecules)
- Electronic configuration 1s22s22p63s23p2
- Valency 4
- Silicon exists in two allotropic forms
- crystalline form
- amorphous form
9. Silicon shows an oxidation state of +4
NOTE: Silicon is a non metal although the electrical properties of Si are like those of a metalloid ( a semiconductor)
EXTRACTION
The element silicon in its crystalline form is extracted by reducing its oxide ( finely powdered sand or quartz) with carbon in an electric furnace. A small amount of iron is added to prevent the formation of Carborundum ( SiC).
SiO2 + 2C è Si (crystalline) + 2CO
And in its amorphous form it is obtained by heating dry powdered silica with magnesium
SiO2 + 2Mg è Si (amorphous) + 2MgO
NOTE: the amorphous allotrope of silicon is much more reactive than the crystalline form. Amorphous silicon is a brownish powder. When amorphous silicon is strongly heated, it fuses an solidifies to the crystalline form. The crystalline form is of a light orange colour
USES OF SILICON
Silicon is used in the manufacture of alloys, such as silicon bronze, manganese silicon bronze, ferrosilicon etc. alloys of silicon posses a very high strength, hardness and are resistant to acids.