Arrange the elements in each of the following groups in increasing order of the most positive electron affinity.
Li,Na,K

Explanation

`K lt Na lt Li.` Electron Affinity decreases down the group as the electropositive character of an element increases. Generally, more non-metallic elements have greater tendency to readily accept electrons. Although most alkali metals are highly electropositive but K is definitely more electropositive than Li. So, down the group electron affinity decreases and hence the order.