Question

Why silicon is hard and brittle while silicone is very soft?

Answer 1

Compared with pure metals and ionic salts, covalent solids such as silicon are hard and brittle because dislocations do not move in them except at high temperatures..silicon is bonded in a giant covalent lattice and has a tetrahedral structure, and is very hard to break apart.

silicones consist of an inorganic silicon-oxygen backbone chain (?-Si-O-Si-O-Si-O-?) with organic side groups attached to the silicon atoms. These silicon atoms are tetravalent. So, silicones are polymers constructed from inorganic-organic monomers.