The difference between bond angle of cationic part and anionic part of solid ${\mathrm{N}}_2{\mathrm{O}}_5$ is :

In N₂O₅, there is one cationic part, ${\mathrm{NO}}_2^{+}$ and one anionic part, ${\mathrm{NO}}_3^{-}.$

${\mathrm{NO}}_2^{+}$ is a nitronium ion that has sp hybridization and a linear shape. Its bond angle is $180°.$ ${\mathrm{NO}}_3^{-}$ is nitrate ion and has sp² hybridization with three bond pairs. Its bond angle is $120°.$

Difference between the bond angle of the cationic and anionic parts of N₂O₅ is $60°\left(180°-120°\right).$