Question

(a) How is possible valency of an element determined from the electronic configuration of its atom ?

(b) Determine the valency of an element X whose atomic number is 15. 

Answer 1

(a) Valency can be determined from no. of electron in the outermost shell. No. of electron in the outermost shell can be observed by writing the electronic configuration. 

(b) X : 2, 8, 5

     15 

Element X has 5 electron in the outermost shell, hence the valency of is 8–5= 3.