Question

Aluminium is usually found in +3 oxidation state. In contrast, thallium exists in +1 and +3 oxidation states. This is due to:

• A. lanthanoid contraction
• B. lattice effect
• C. diagonal relationship
• D. inert pair effect

Answer 1

The correct option is D inert pair effect

Inert pair effect is the prominent character of the p-block element.
In this, the high molecular weight element of the group show a lower oxidation state.

This is because on going down the group, the shielding effect increases, but d-subshell and f-subshell shown poor shielding effect.

Thus, high molecular weight members of p-block groups contains d-subshell and f-subshell has lesser shielding effect. Because of this, they show a lower oxidation state.

Hence, optionn D is correct.