Which of the following is NOT a physical or chemical characteristics of interstitial compounds?
- They have high melting points, higher than those of pure metals.
- They are very soft and ionic in nature.
- They retain metallic conductivity.
- They are chemically inert and usually non-stoichiometric.
Answer
(2) They are very soft and ionic in nature.
Solution
As per NCERT, interstitial compounds (small atoms like H, C, N trapped in the metal lattice, e.g. TiC, Mn4N, Fe3H) have these characteristics:
(i) high melting points, higher than those of pure metals – (1) is true
(ii) very hard (some borides approach diamond in hardness) – so (2) "very soft and ionic" is NOT true; they are neither typically ionic nor covalent
(iii) they retain metallic conductivity – (3) is true
(iv) chemically inert and usually non-stoichiometric – (4) is true
Answer: (2)