Diamond is a structure of carbon (on Face Centre lattice point and Alternate Tetrahedral Void ) which has approx 66% empty . How it hardest substance on earth ?
Solution:
Though Diamond contains covalent bonds, all the C-atoms are attached to four other C-atoms by σ-bond and so they exist as sp3 hybridized atoms.
The above sp3 hybridized atoms are attached tetrahedrally in three-dimensional form, which makes the structure very rigid and strong. Hence, the diamond is the hardest substance.