Question

Explain why transition metals form complex compounds.

Answer 1

Hint: The d-block elements are called transition elements in the long form of periodic table. Coordination compound is defined as any class of substances with chemical structures in which a central metal atom is surrounded by non metal atoms joined to it by chemical compounds.

Complete step by step answer:
The position of d-block elements are in between s-block and p-block elements in periodic table. These d-block elements are called transition elements because they exhibit transitional behavior between s-block and p-block elements. Their properties are transitional between highly reactive metallic elements of s-block which are ionic compounds and elements of p-block which are largely covalent.
Transition metals are d-block elements with valence shell configuration $n{s}^2(n-1)d^{1-10}$. The transition metals and their ions easily coordinate to a number of negative ions or neutral molecules having lone pairs of electrons to form complexes. The reason for this is small size and high nuclear charge of these metals and availability of vacant d-orbitals of suitable energy to accommodate lone pairs of electrons donated by the ligands. The cations of the d-block elements have a strong tendency to form complexes with certain molecules or ions called ligands. Some examples of transition metal complexes are $[Cu(N{H}_3{)}_4{]}^{2+},[Ag(N{H}_3{)}_4{]}^{+},[Fe(CN{)}_6{]}^{4-}$ etc. Most transition metals can be bound to a variety of ligands, allowing for a wide variety of transition metal complexes.

Note: Transition metals are also defined as the elements with partially filled d-subshell. Zinc, cadmium and mercury are not considered as transition metals as they have fully filled electrons in its d-orbital. Transition metals are small in size and have high positive charge density of ions.