An electron withdrawing group (EWG) will have the opposite effect on the nucleophilicity of the ring. The EWG removes electron density from a π system, making it less reactive in this type of reaction, and therefore called deactivating groups.

Do electron donor groups increase reactivity?

An electron donating group (EDG) has the net effect of increasing electron density in a molecule through the carbon atom it is bonded to. By increasing electron density on adjacent carbon atoms, EDGs change the reactivity of a molecule: EDGs make nucleophiles stronger.

What is the effect of electron withdrawing group on the reactivity of Haloarenes?

The presence of electron withdrawing group increases the reactivity of haloarenes. The effect is more pronounced at ortho and para position. From resonance structure of chlorobenzene we see that electron density is maximum only at o/p-position. So, it does not affect much at w-position.