Which of the halide ions (f−, cl−, br−, and i−) is the most stable base? which is the least stable base?

Explanation:

It is known that on moving down a group there will occur a decrease in electronegativity of non-metals. Whereas stability of their conjugate bases increases on moving down the group.

This also means that their acid strength also increases.

For example,

where, X = F, Cl, Br or I)

Therefore, acidity will increase in the following order.

                      HI > HBr > HCl > HF

Hence, the stability of their conjugate bases will be as follows.

Thus, we can conclude that the most stable base is and least stable base is .

the answer is c.the valence of the atoms combine .