Which of the following orders are correct as per the properties mentioned against each? 

(i) As₂O₃ < SiO₂ < P₂O₃ < SO₂               Acid strength. 

(ii) AsH₃ < PH₃ < NH₃                             Enthalpy of vapourisation. 

(iii) S< O < Cl <  F                                    More negative electron gain enthalpy. 

(iv) H₂O  > H₂S  > H₂Se  > H₂Te             Thermal stability.

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.