Explain why the EN's of Ga, In and `TI` do not vary much though they are expected to decrease in the group.

Explain why the planets do not twinkle?

Explain why HCl is a gas and HF is a liquid ?

Explain why : Rivers and lakes do not freeze easily?

Explain why some planets do not have atmosphere.

Why do you think the noble gases are placed in a separate group?

Explain why the speed of sound through a gas cannot be greater than the r.m.s. speed of the molecules of the gas.

Explain why raindrops falling under gravity do not acquire high velocity.

Why does the ionisation energy decrease on going down a group?

Explain why the reactance provided by a capacitor to an alternating current decreases with increasing frequency.

Why do elements with similar properties occur in the same group?