Assigns reasons for the following:
(i) Transition metals exhibit enthalpy of atomisation.
(ii) Transition metals form interstitial compounds.

(i) Transition metal has high heat of atomisation due to presence of strong metallic bond which arises due to presence of unpaired electron in the (n - 1) d subshell. This is because the atoms in these elements are closely packed and held together by strong metallic bonds. The metallic bond is formed as a result of the interaction of electrons in the outermost shell. Greater the number of valence electrons, stronger is the metallic bond.

ii)Transition metals often have close packed (ccp, hcp) lattices that have N oct interstices (holes) for N close packed metal atoms. 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, VH_0.56 and TiH_1.7, etc.