Isc 2 a − Profile

4

-1/3

a)

It is an amporphous solid

On heating ZnO, some some anions leave the lattice. But as they go, to keep charge neutral, they leave behind an electron. This trapped electron can excite and de-excite in available energy levels, and in doing so, imparts yellow colour to the salt. This is called metal excess defect as metal ions are left in excess of anions and the extra electrons form colour centres or f - centres.

degree of dissociation=78.12%(0.7812)

41.5 g/cm³

In a counductor the conduction band overlaps with the valance band or the valance band is partially filled which allows the movements of e. In a semi-conductor the valance and conduction band have a small gap. Conductor-Cu, Semi-conductor-Si