Question

An element X belongs to group 2 and another element Y belongs to group 15 of the periodic table:

(a) What is the number of valence electron in X?
(b) What is the valency of X?
(c) What is the number of valence electrons in Y?
(d) What is the valency of Y?
Explain how you have arrived at your answers.

Answer 1

(a) The number of valence electrons in element X is 2 because this element belongs to group 2.

(b) The valency of the group 2 element X is 2.

(c) Valence electrons of group 15:
Group number = Valence electrons + 10
                 15 = Valence electrons + 10
Valence electrons = 15 - 10 = 5           

(d) Valency of the group 15 element Y is 3, that is, (8 - 5).