Question

Which of the following statement is incorrect with regard to interstitial compounds of transition elements?

• A. They have high melting points.
• B. They are very hard.
• C. They have metallic conductivity.
• D. They are chemically inert.
• E. They are stoichiometric compounds.

Hint:

Interstitial compounds of transition elements are generally non-stoichiometric, meaning the ratio of atoms is not fixed, unlike typical ionic compounds that have fixed stoichiometry.

Answer 1

Answer: (E)

Interstitial compounds are compounds formed when small atoms, such as hydrogen, carbon, or nitrogen, occupy interstitial spaces (gaps) in the crystal structure of metals, particularly transition elements. These compounds typically exhibit the following properties:
- (A) They have high melting points. This is true. Interstitial compounds tend to have high melting points due to the strong bonding between the metal atoms and the interstitial atoms.
- (B) They are very hard. This is also true. Interstitial compounds are usually hard due to the presence of small atoms occupying the interstitial sites, which increases the overall strength of the structure.
- (C) They have metallic conductivity. True. Despite the interstitial atoms, these compounds often maintain metallic conductivity, as the overall metallic lattice structure is retained.
- (D) They are chemically inert. This is true. Interstitial compounds tend to be chemically inert, as the interstitial atoms do not easily react due to the close-packed nature of the metal structure.
- (E) They are stoichiometric compounds. This is incorrect. Interstitial compounds are typically non-stoichiometric because the number of interstitial atoms can vary, making the stoichiometric ratio not fixed.
Thus, the incorrect statement is (E) They are stoichiometric compounds.