Question

The elements Li(Z = 3), Na (Z = 11)and K (Z = 19) belong to group 1

(i) Predict the periods they belong.

(ii) Which one of them is least reactive?

(iii) Which one of them has the largest atomic radius? Give reason to justify.

Answer 1

As we already know that number of valence electrons is equal to its group number. Here, all of them have only one electron in their valence shell hence, they belong to First group.

Lithium is less reactive due to its smallest size and more ionization energy.
Among the three K has the large atomic radius  because it has more  number of shells.