Question

Which amongst the following atoms does not have a valency of one?

• A. Hydrogen
• B. Oxygen
• C. Sodium
• D. Chlorine

Answer 1

The correct option is B Oxygen

Valency is the combining capacity of an element. It is determined by the number of valence electrons. Valency can be calculated from a short-cut method given below.

1. For the atoms having less than four valence electrons, valency = number of valence electrons
2. For the atoms having more than four valence electrons, valency = (8 - no. of valence electrons)

$$\begin{array}{cccc}\text{Element}& \text{Electronic configuration.}& \text{Valence electrons}& \text{Valency}\\ \text{Hydrogen}& \text{1}& \text{1}& \text{1}\\ \text{Oxygen}& \text{2,6}& \text{6}& \text{8 - 6 = 2}\\ \text{Sodium}& \text{2,8,1}& \text{1}& \text{1}\\ \text{Chlorine}& \text{2,8,7}& \text{7}& \text{8 - 7 = 1}\end{array}$$
Thus, only oxygen out of given options does not have valency 1.