Question

The elements Li, Na and K, each having one valence electron, are in period 2, 3 and 4 respectively of modern periodic table.

(i) In which group of the periodic table should they be ?

(ii) Which one of them is least reactive ?

(iii) Which one of them has the largest atomic radius ? Give reason in justify your answer in each case.

Answer 1

Electronic configuration of Li, Na and K can be written as:

Li → 2, 1

Na → 2, 8,1

K → 2, 8, 8, 1

(a) As all of them have only on electron in their valence shell they belong to Group 1.

(b) Li is the least reactive among them due to its smallest size as it has only 2 shells.

(c) K has the largest atomic radius among the three because it has maximum number of shells.

Higher the number of shells, larger is the atomic radius.