It is because of inability of ns² electrons of the valence shell to participate in bonding that

HClO₄ is the most acidic compound.

Group number = 11 (Atomic number = 111)

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.

Reducing character increases from NH₃ to BiH₃.

Group 15 oxides of type E₂O₃ and E₂O₅ are not always basic.