Solution

Benzene is a planar molecule having delocalized electrons above and below the plane of ring. Hence, it is electron-rich. As a result, it is highly attractive to electron deficient species i.e., electrophiles.

Therefore, it undergoes electrophilic substitution reactions very easily.

In nitration of benzene,the electrophile is the "nitronium ion" or the "nitryl cation".This is formed by reaction between the nitric acid and the sulphuric acid.