Question

Discuss the important characteristics of the hydrides of group 16 elements.

Answer 1

1. They have an angular shape due to sp³ hybridisation of the central atom (e.g., H₂O).
2. Bond angle decreases down the group \[\ce{H - O - H (104.5°) > H - S - H > H - Se - H > H - Te - H}\].
3. Boiling points increase down the group due to increasing Van der Waals forces.
4. Thermal stability decreases down the group H₂O > H₂S > H₂Se > H₂Te.
5. Acidic strength increases down the group H₂O < H₂S < H₂Se < H₂Te.
6. Except for H₂O, hydrides act as reducing agents, and reducing power increases down the group.

These hydrides behave as weak diprotic acids and have polar \[\ce{M - H}\] bonds that dissociate in aqueous solution, forming H₃O⁺ ions. H₂O is the most stable due to hydrogen bonding, while others have weaker \[\ce{M - H}\] bonds.