Consider the following statements about interstitial compounds and alloys of the transition metals.
(A) Interstitial compounds are formed when small atoms like H, C or N are trapped inside the crystal lattices of metals.
(B) Interstitial compounds such as TiC and Mn4N are typically ionic in nature.
(C) Alloys that are homogeneous solid solutions are formed by atoms with metallic radii that are within about 15 percent of each other.
(D) Bronze is an alloy of copper and zinc.
Which of the statements given above are correct? Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A) and (C) only
Transition metals take small non-metal atoms into the spaces of their lattices (interstitial compounds) and mix readily with other metals of similar size (alloys).
(A) Interstitial compounds are formed when small atoms like H, C or N are trapped inside the crystal lattices of metals. — True. The small atoms sit in the interstices (holes) of the metal lattice, which is why these compounds are called interstitial.
(B) Interstitial compounds such as TiC and Mn4N are typically ionic in nature. — False. These compounds are neither typically ionic nor covalent. They are usually non-stoichiometric, and their formulas do not match any normal oxidation state of the metal.
(C) Alloys that are homogeneous solid solutions are formed by atoms with metallic radii that are within about 15 percent of each other. — True. The atoms of one metal can take random places among the atoms of the other only when their sizes are similar. Transition metals have similar radii, so they form alloys readily.
(D) Bronze is an alloy of copper and zinc. — False. Bronze is an alloy of copper and tin. The alloy of copper and zinc is brass.
NCERT (2026-27 edition):
4.3.13 Formation of Interstitial Compounds – “Interstitial compounds are those which are formed when small atoms like H, C or N are trapped inside the crystal lattices of metals. They are usually non stoichiometric and are neither typically ionic nor covalent, for example, TiC, Mn4N, Fe3H, VH0.56 and TiH1.7, etc.”
4.3.14 Alloy Formation – “…Alloys may be homogeneous solid solutions in which the atoms of one metal are distributed randomly among the atoms of the other. Such alloys are formed by atoms with metallic radii that are within about 15 percent of each other. … Alloys of transition metals with non transition metals such as brass (copper-zinc) and bronze (copper-tin), are also of considerable industrial importance.”