Account for the following:
(a)    Transition elements have high boiling point and high enthalpy of atomisation.
(b)    Zn, Cd, Hg are normally not regarded as transition elements.
(c)    Transition metals generally form alloys with other transition metals.
(d)    Transition metals form a number of interstitial compounds.
(e)    Ni²⁺ compounds are thermodynamically more stable than Pt²⁺ compounds.

a) The melting points of transition elements are high due to the presence of strong intermetallic bonds (formed by valence electrons) and covalent bonds (formed due to d-d overlapping of unpaired d-electrons). 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.

b) The electronic configurations of Zn, Cd and Hg are represented by the general formula (n-1)d10ns2. The orbitals in these elements are completely filled in the ground state as well as in their common oxidation states. Therefore, they are not regarded as transition elements.

c) An alloy is a blend of metals prepared by mixing the components. Alloys may be homogeneous solid solutions in which the atoms of one metal are distributed randomly among the atoms of the other. Such alloys are formed by atoms with metallic radii that are within about 15 percent of each other. Because of similar radii and other characteristics of transition metals, alloys are readily formed by these metals.

d) The transition metals appear to be unique in their ability to react with small atoms of non- metal to give interstitial compound. These  metals form various interstitial compound in which small non- metal like H,C,B,N and He occupy the empty space in their lattice and also form bond with them.

e) Ni²⁺ is smaller in size and thus has smaller the ionization enthalpy of a metal greater thermodyanmic stability of its compound.