${\mathrm{CO}}_2$ is non-polar while ${\mathrm{SO}}_2$ and ${\mathrm{H}}_2\mathrm{O}$ are polar. Explain.

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?