Question

What are interstitial compounds? Why do these compounds have higher melting points than corresponding pure metals?

Answer 1

Interstitial compounds: They are those compounds of the transition metals which are formed when small atoms like $H,C$ or $N$ are trapped inside the interstitial vacant spaces in the crysal lattices of the metals. Some of the examples of interstitial compounds are $TiC$, $Ti{H}_{1.73}$, $M{n}_4$N, $F{e}_{3}H$ etc.
The interstitial compounds have high melting point due to the following reasons.
$\bullet$ They are very hard.
$\bullet$ They are chemically inert, and
$\bullet$ The presence of the foreign atoms stablizes the crystal structure.