Why is density of silicon less than carbon
The large macromolecular structure of carbon allows for close packing of carbon atoms making them more dense. In silicon even though the structure is macromolecular, due to its atoms large size, it cannot pack as closely as carbon thus having a lower density than carbon.
Silicon is abundant metal in the world
Silicon is neither metal nor non metal. its a metalloid. Aluminium is the most abundant metal in earth