Give reason- While going down in group 1 lithium is least electropositive while caesium is most electropositive.

Explanation

As we move down in a group, an electron shell is aded after every change of period. For example, lithium has only two electron shells around the nucleus, but caesium has six electron shells around the nucleus. Thus, the positive charge within the nucleus holds the valence electrons of lithium more strongly than caesium. In other words the valence electrons are held very loosely in case of caesium than lithium. Thus, caesium can lose its valence electrons more easily and hence, is more electropositive as compared to lithium, which is less electropositive. In other words, caesium is more metallic in character than lithium.