Which of the following is not the property of interstitial compound

Interstitial compounds are those that are created when tiny H, C, or N atoms become trapped inside the metal crystal lattice. The transition metals can combine to generate a variety of interstitial compounds.

Characteristics:

(i) They have high melting points.

(ii) They are very hard.

(iii) They retain metallic conductivity.

(iv) They are chemically inert.

Hence, the correct option is (D) .