Which of the following statements are correct? 

(i) Among halogens, the radius ratio between iodine and fluorine is maximum. 

(ii) Leaving the F—F bond, all halogens have weaker X—X bonds than X—X'bonds in interhalogens. 

(iii) Among interhalogen compounds maximum number of atoms are present in iodine fluoride. 

(iv) Interhalogen compounds are more reactive than halogen compounds.

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.