Which of the following ions will form the weakest bond with Na+?
Br^-
F^-
CI^-
I^-

Iodide ion, I- will form the weakest bond with sodium ion, Na+

Explanation:

Electronegativity is the ability with which a neutral atom attracts electrons to itself.

The electronegativity of the halogens decrease on going down the group among the halogens. This is is because on going down the group, the atomic size as well as ionic size of the atoms in the group increases. This increase decreases the effect of the attraction of the positive nucleus on the electrons. Thus, valence electrons can be more readily removed.

The transfer of electrons from metallic sodiummto a halogen results in annionic bond between the two atoms. The strength of the ionic bond decreases on going down the group due to decrease in electronegativity. Thus, iodide ion, I-, which is the least electronegative among the given options will form the weakest bond with Na+.