Silicon is the chemical element of the periodic table of the elements that has the symbol Si with valence 2,4,6 and as atomic number 14. It is a semi-metal and a tetravalent semiconductor, silicon is less reactive than its chemical analogue, carbon . It is the second element for abundance in the earth's crust after oxygen, composing 27.7% of the weight. It is found in clay, feldspar, granite and quartz, mainly in the form of silicon dioxide, silicates and alumino silicates (silicon containing compounds, oxygen and metals). Silicon is the main component of glass, cement, ceramics and silicon.