i) What are F-centres in an ionic crystal?

(ii) Why are crystals having F-centres paramagnetic?

22. The central atom of methane and water is in the same state of hybridization, but the shapes of the two molecules are different. Discuss.

For a crystal of diamond, state:

(i) The hybridisation of the carbon atom.

(ii) The coordination number of each carbon atom.

(iii) The type of lattice in which it crystalises.

(iv) The number of carbon atoms present per unit cell.

Write the formulae of the following coordination compounds:

(i) potassiumtetracyanonickel(II)

(ii) triamminetrinitrocobalt(III)

[CoF₆]^3- is a coordination complex ion.

(i) What is the oxidation number of cobalt in the complex?

(ii) How many unpaired electrons are there in the complex?

(iii) State the magnetic behaviour of the complex.

(iv) Give the I.U.P.A.C. name of the complex.