Question

Account for the following : (a) BiH3 is the strongest reducing agent in Group 15 elements hydrides.

Answer 1

The reducing character of the hydrides of Group 15 elements increases from NH3  to BiH3(Bismuthine) because the reducing character depends upon the stability of the hydride.The greater the unstability of anhydride,the greater is the its reducing character.Since,the BiH3 is the least stable (because the size of central atom is greatest & therefore its tendency to form stable covalent bond with small hydrogen atom decreases,as a result the bond strength decreases) in this series,hence the reducing character increases.

Answer 2

Answer:

• As we move down a group, the atomic size increases and the stability of the hydrides of group 15 elements decreases.
• Since the stability of hydrides decreases on moving from NH3 to BiH3, the reducing character of the hydrides increases on moving from NH3 to BiH3.