Answer:
B. Br-
Explanation:
Ionic radius is a way of measuring the size of an element or compound.
Ionic Radius
Ionic radius is defined as the distance between the nucleus of an atom and the outermost electron. In terms of the periodic table, ionic radius grows to the left and down. The largest element on the periodic table is Francium since it is the lowest element on the left side.
Effective Nuclear Charge
The ionic radius of cations (positive ions) is always smaller than the regular element. Also, the ionic radius of anions (negative ions) is always larger. This is due to effective nuclear charge. Effective nuclear charge is how attracted electrons are to the nucleus. As electrons are added, effective nuclear charge decreases as the shielding effect becomes larger. Additionally, as the negative charge increases, the positive charge has less pull. The opposite is true for cations.
Since the electrons are less attracted to the nucleus in anions, they spread out more. This causes the radius to increase. For this reason, Br- has the largest ionic radius out of the listed options.
