Define electropos

State the reason behind the observed trend in the above elements.

Electropositivity is the measure of the ability of elements (mainly metals) to donate electrons to form positive ions. Example Li⁺, Na⁺, K⁺.

OR

As we move down in a group, addition of new shells occurs which increases the distance between nucleus and valence electrons thereby decreasing the pull effect of nucleus on the valence electrons, resulting in the increase in atomic radius of the atom.