which of the following are aromatic compounds?

i)

ii)

iii)

iv)

Aromaticity is due to the 

• Planarity
• Complete delocalization of the pi electrons in the ring
• Presence of (4n+2 )$\mathrm{\pi }$electrons in the ring

(1) Napthalene 

n=2 

Huckel'rule :(4n+2 )$\mathrm{\pi }$electrons

=4(2) +2 $\mathrm{\pi }$electrons = 10$\mathrm{\pi }$electrons

(2) Benzene :

n=1

Huckel'rule :(4n+2 )$\mathrm{\pi }$electrons

=4(1) +2 $\mathrm{\pi }$electrons = 6$\mathrm{\pi }$electrons

so these two molecules are Aromatic.