Interstitial transition metal compounds
(A) have higher melting points than those of pure metals.
(B) have more reactivity than those of pure metals.
(C) are non-stoichiometric compounds.
(D) formed when small atoms like H, C or N are trapped inside the crystal lattice of the metals.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (C) and (D) only
Interstitial compounds are formed when small atoms such as H, C or N are trapped in the empty spaces (interstices) of the crystal lattice of a transition metal, as in TiC, \( \ce{Mn4N} \), \( \ce{Fe3H} \) and \( \ce{TiH_{1.7}} \). Their formulas do not correspond to any normal oxidation state of the metal.
(A) have higher melting points than those of pure metals. — Correct. The small atoms bind the metal atoms more firmly, so these compounds melt at higher temperatures than the pure metals and are very hard.
(B) have more reactivity than those of pure metals. — Incorrect. Interstitial compounds are chemically inert; they are less reactive, not more.
(C) are non-stoichiometric compounds. — Correct. The number of trapped atoms varies, so the composition is not fixed by valency, as in \( \ce{VH_{0.56}} \).
(D) formed when small atoms like H, C or N are trapped inside the crystal lattice of the metals. — Correct. This is the definition of an interstitial compound.
NCERT (2026-27 edition):
Formation of Interstitial Compounds
