Question

Identify the correct pair of elements and their valency.

• A. Nitrogen-3
• B. Oxygen-2
• C. Carbon-3
• D. Sodium-2

Answer 1

Answer: (A), (B)

The correct options are
A Nitrogen-3
B Oxygen-2

The combining capacity of an element is known as its valency. It is determined by the number of valence electrons present in the outermost shell of an atom. The table given below shows the valency of the elements mentioned in the options.
$$\begin{array}{cccc}\text{Element}& \text{Atomic no.}& \text{Electronic configuration}& \text{Valency}\\ \text{Nitrogen}& \text{7}& \text{2, 5}& \text{3}\\ \text{Oxygen}& \text{8}& \text{2, 6}& \text{2}\\ \text{Carbon}& \text{6}& \text{2, 4}& \text{4}\\ \text{Sodium}& \text{11}& \text{2, 8, 1}& \text{1}\end{array}$$ Hence, the correct pair is nitrogen-3 and oxygen-2.