Question

(a) Based on the nature of intermolecular forces, classify the following solids:
Silicon carbide, Argon
(b) ZnO turns yellow on heating. Why?
(c) What is meant by groups 12 - 16 compounds? Give an example.

Answer 1

(a) (i) Silicon carbide $\to$ Covalent network solid (covalent bonding)
(ii) Argon $\to$ Non - polar molecular forces which possess London dispersion forces.
(b) On heating, ZnO losses oxygen and turns yellow. This is due to the temporary creation of F-centres.
$ZnO\stackrel{\text{Heat}}{\to }Z{n}^{2+}+\frac{1}{2}{O}_2+2e^{-}$
(c) In these compounds, bonds have some ionic character along with covalency. The percentage ionic character depends upon the electronegativities of the two atoms.
Ex: ZnS, CdSe, HgTe.