Question

Which is a better nucleophile, a bromide ion or an iodide ion?

Answer 1

Bromide because it is more stable than iodide

Answer 2

Answer: Iodine is a better nucleophile.

Explanation:

Nucleophiles are the substances which can easily donate a pair of electron.

As we move down the group of halogens, size of atoms increases and hence electronegativity decreases.

Iodine is least electronegative in halogens. Therefore, it can easily donate a pair of electron and hence becomes a better nucleophile.

Whereas, bromine is small in size as compared to iodine so it will hold the electrons more tightly. Hence, it is difficult for bromine to lose electrons.

Thus, it can be concluded that out of bromine and iodine, iodine is a better nucleophile.