Sudanshu made a model of the unit cell of diamond. It resembled the unit cell of ZnS. If the unit cell of ZnS has 4 units of ZnS per unit cell. It has the same packing efficiency as ZnS. But diamond is the hardest known substance.
(a) What is the number of atoms of carbon per unit cell of diamond?
(b) Why diamond is the hardest known substance?
(c) What is the value that Sudanshu can derive from these facts?

Explanation

(a) The number of atoms of Carbon per unit cell is 8 in diamond.
(b) The C—C bond is very strong in diamond (due to small size of Carbon) unlike the Zn—S bond in ZnS.
(c ) Though from the same background i.e. with the same structure the property can be different, thus, with a little effort, we can do same things differently and bring about major changes.