JEE Main · 2013 · 07 Apr 2013 · Offline · Solid State

A covalent, or network, solid is laced throughout by covalent bonds into a single giant lattice. Silicon does exactly this, each atom bonded tetrahedrally to four neighbours in a diamond-like framework. Sulphur ($\mathrm{S}{}_8$), phosphorus ($\mathrm{P}{}_4$) and iodine ($\mathrm{I}{}_2$) exist instead as discrete molecules held to one another only by weak van der Waals forces, so silicon is the covalent crystal.