What is the difference between 13-15 and 12-16 compounds?

1

(a)

Group 13-15 compounds such as AIP, GaAs, ect.have large covalent character but Group 12-16 compounds such as ZnS, cDs,HgTe, etc. do not have perfect covalent bonds but possess sufficient ionic character. However, all of them are semiconductors.

What is F-centre?

1

(a)

The site where electron is entrapped in the anion vacancy is called F-centre.

Name the type of point defect that occurs in a crystal of zinc sulphide.

1

(a)

Frenkel defect

Which point defect in crystals of a solid does not change the density of the solid?

1

(a)

Frenkel defect

What happens when a ferromagnetic or anti-ferromagnetic or a ferrimagnetic solid is heated?

1

(a)

It changes into paramagnetic at some temperature.