Question

Why do transition elements form complexes?

Answer 1

The elements in the d-block of the periodic table are known as the transition elements or transition metals. The d-block occupies the central part of the periodic table from group-3 to group-12.

Complete answer:
The valence shell electronic configuration of transition metals is $n{s^2}\left( {n - 1} \right)d$.
Both the electrons of $ns$ shell and the electrons of $\left( {n - 1} \right)d$ shell participate in the bonding.
The transition metals and the ions of transition metals coordinate easily to many negative ions or neutral molecules having ion pairs of electrons and form complexes.
This is because:
- Transition metals have small size.
- Transition metals have high nuclear charge.
- Transition metals have d-orbitals vacant to accommodate the lone pairs of electrons donated by the ligands.
Some examples of transition metals are: scandium, titanium, zinc, yttrium, cadmium, iron, cobalt, nickel, silver, gold, platinum, mercury, manganese, etc.

Additional Information: Transition metals are rough and hard in nature.
Transition metals are good conductors of electricity and heat. Transition metals have high melting points (except for mercury which is liquid at room temperature), high boiling points and high densities. Transition metals are paramagnetic and form coloured compounds.
Transition metals exhibit variable oxidation states, also they have an ability to interchange between the oxidation states and can form complexes with the reagents. Due to these reasons, transition metals act as a good source of electrons and thus, act as catalysts.

Note: Transition metals exhibit variable oxidation states, also they have an ability to interchange between the oxidation states and can form complexes with the reagents. Due to these reasons, transition metals act as a good source of electrons and thus, act as catalysts.