List some drawbacks of Mendeleev's periodic table.

An element $\mathrm{X}$ belongs to group $\mathrm{I}$ and third period of the periodic table. Find out:

(i) electron arrangement.

(ii) metal or non-metal.

(iii) name of the element.

Which has the larger atomic radius?

$\mathrm{Na}$ or $\mathrm{K}$

Which has the larger atomic radius?

$\mathrm{F}$ or $\mathrm{Cl}$

Which has the larger atomic radius?

$\mathrm{S}$ or $\mathrm{P}$

Which has the larger atomic radius?

$\mathrm{O}$ or $\mathrm{S}$