The electron donating and withdrawing strength of each of the given groups,- NO2 and – NH2is depending on each the inductive effect in addition to mesomeric effect/resonance.It can be elaborated as follows:
i)In – NO2,the N has a +ve charge since its lone pair(lp) has already been coordinated to O,making the lp unavailable for donation to any other group/ring.Since N already has a +ve charge,it tends to pull e- density towards itself,by means of both resonance(-R) as well as inductive effect(-I).
Making – NO2overall as an e- withdrawing group(EWG).
ii)On the contrary,in – NH2,N has its lp free on itself,that it can donate to any ring by means of resonance(+R effect).Also N being more EN than C,tends to pull e- density away from the ring/group and towards itself,contributing to its inductive(-I) effect.However,taking into account the fact that resonance is a stronger phenomenon than inductive effect,the overall nature of
-NH2 is that of an electron donating group(EDG).
Final Answer:
Hence,NH2 has a strong e- donating power courtesy dominance of +R over -I while – NO2has a strong e- withdrawing power attributed to -I and -R.