Bond dissociation enthalpy of E—H (E = element) bonds is given below. Which of the compounds will act as the strongest reducing agent? 

Compound NH₃ PH₃ AsH₃ SbH₃ 

Δdiss(E---H)/kJ mol--1 389          322       297         255

(i) NH₃

(ii) PH₃

(iii) AsH₃

(iv) SbH₃

HClO₄ is the most acidic compound.

Group number = 11 (Atomic number = 111)

Heavier element of p block do not from pπ− pπ bonds as their atomic orbital are so large and diffius that they cannot have effecitve overlapping.

The inertness of ? subshell electrons towards bond formation is known as inert pair effect. This effect increases down the group thus, for Sn,  oxidation state is more stable, whereas, for Pb,  oxidation state is more stable, i.e.,  is reducing while  is oxidising.