Question

How does the inert pair effect affect the properties of group 15 elements?

Answer 1

1. The inert pair effect is the reluctance of the ns² electron pair in the valence shell to participate in bonding, especially in heavier group 15 elements like Sb and Bi.
2. Due to this effect, the stability of the +3 oxidation state increases down the group, while the +5 oxidation state becomes less stable.
3. Antimony and bismuth predominantly show the +3 oxidation state by losing only the np³ electrons, keeping the ns² pair inert.
4. The inert pair effect causes the lower melting points of Sb and Bi than expected because these elements form fewer bonds (three instead of five), weakening interatomic attractions.
5. Because of the effect, bismuth forms mostly Bi³⁺ ions, and compounds with +5 oxidation state are rare and usually covalent.
6. Overall, the inert pair effect influences oxidation states, bonding, and physical properties (like melting points) of heavier group 15 elements.