In which of the following molecule, is the London force likely to be most important in determining $\mathrm{m}.\mathrm{p}.$ and  $\mathrm{b}.\mathrm{p}.$ and why?

$\mathrm{ICl}, {\mathrm{Br}}_2, \mathrm{HCI}, {\mathrm{H}}_2$ and $\mathrm{CO}$.

Give total number of $\mathrm{\sigma }$ and $\mathrm{\pi }$ bonds in,

(a) ${\mathrm{C}}_6{\mathrm{H}}_6$

(b) ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{OH}$

(c) ${\mathrm{C}}_7{\mathrm{H}}_8$

Write formal charge of all the atoms in:

(a) ${\mathrm{CO}}_3^{2-}$ ion

(b) ${\mathrm{NO}}_2^{-}$ ion

Sodium metal vaporises on heating and the vapours have diatomic molecules of sodium (Na₂). What type of bonding is present in these molecules?