Question

Give reason :
(i)ZnO crystal on heating acquires the formula `Zn_(1+x)O`.
(ii)There is an increase in conductivity when Silicon is doped with Phosphorus.

Answer 1

(i)On heating ZnO loses oxygen as `ZnO to Zn^(2+) + 1/2 O_2 + 2e^-`
Excess `Zn^(2+)` ions are entrapped into vacant interstitial sites. Hence, there is metal excess.
(ii)Silicon belongs to Group 14 while phosphorus belongs to Group 15. Hence, in the valence shell, P has one extra electron than Si. When Si is replaced by P atom, due to extra electron, there is increase in conductivity.