Some d-block metals, such as titanium, vanadium, zirconium, niobium, hafnium, and tantalum, react with nitrogen at high temperatures to form nitrides with the formula MN (in which M is the metal). The compounds are very hard, have high melting points, and have high electrical and thermal conductivities.

The atoms are arranged in the same way as in NaCl (Topic 3H).

(a) Would you classify these compounds as alloys, salts, molecular solids, or network solids? Justify your answer.

(b) What is the evidence for covalent character in the bonding of these compounds?

(c) Use electron configurations to explain why metals in Groups 11 and 12 do not form these types of nitrides.