For each of the following pairs which has greater `IE` and why?
a. `Li, Li^(o+)` , b. `K, Br` , c. `Br, I` , d. `Na^(o+) , Ne`

Explanation

a. `Li^(o+)`. Because the size of `Li^(o+)` is smaller and `Z_(eff)` is greater than the corresponding values of `Li`.
b. `Br`. Because `Br` has seven electrons in the outermost shell and has tendency to gain an electron rather than losing it. Moreover, the smaller size and high nuclear charge favour high `IE` for `Br`.
c. `Br`. It is due to the smaller atomic radius of `Br` than that of `I`.
d. `Na^(o+)`. As it has small atomic radius and high value of `Z_(eff)` than `Ne`.