In a cyclotrimetaphosphoric acid molecule, how many single and double bonds are present? 

(i) 3 double bonds; 9 single bonds 

(ii) 6 double bonds; 6 single bonds 

(iii) 3 double bonds; 12 single bonds 

(iv) Zero double bonds; 12 single bonds

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.