Question

Which of the following is not an interstitial compound?

• A. $Sc_2O_3$
• B. TiC
• C. $Mn_4N$
• D. $TiH_{1.7}$
• E. $Fe_3H$

Hint:

Interstitial compounds often retain metallic conductivity and high hardness.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
This question asks to identify which of the given compounds is not an interstitial compound. We need to understand the definition and characteristics of interstitial compounds.
Step 2: Detailed Explanation:
- Interstitial Compounds: These are compounds that are formed when small non-metal atoms (like hydrogen, boron, carbon, nitrogen) are trapped inside the crystal lattice of a metal, occupying the "interstices" or empty spaces between the metal atoms. They are typically formed by transition metals. Key characteristics include being non-stoichiometric (having variable composition), very hard, having high melting points, and retaining metallic conductivity. Let's analyze the options: - (B) TiC (Titanium Carbide), (C) Mn\(_4\)N (Manganese Nitride), (D) TiH\(_{1.7}\) (Titanium Hydride), (E) Fe\(_3\)H (Iron Hydride): These are all classic examples of interstitial compounds. They consist of a transition metal (Ti, Mn, Fe) and a small non-metal atom (C, N, H) that fits into the metallic lattice. Note the non-stoichiometric formula for titanium hydride (TiH\(_{1.7}\)), which is a common feature. - (A) Sc\(_2\)O\(_3\) (Scandium(III) Oxide): This is an oxide of scandium. Oxygen atoms are generally too large to fit into the interstitial sites of metal lattices. Oxides are typically considered ionic or covalent compounds, not interstitial compounds. They form a distinct crystal lattice structure involving both metal cations and oxide anions, and they are stoichiometric. Scandium oxide is a stable, stoichiometric ionic oxide. Step 3: Final Answer:
Sc\(_2\)O\(_3\) is not an interstitial compound; it is an ionic oxide.