Question

Which amongst the following pairs is not an example of molecule?

• A. Oxygen gas and water
• B. Sodium and potassium
• C. Oxygen gas and ammonia
• D. Hydrochloric acid and water

Answer 1

The correct option is B Sodium and potassium

Molecules are formed by the combination of two or more atoms. Given below are few molecules along with their constituent atoms.
$$\begin{array}{cc}\text{Molecule}& \text{Constituent atoms}\\ O_2& \text{2 O}\\ H_{2}O& \text{2 H, 1 O}\\ N{H}_3& \text{1 N, 3 H}\\ HCl& \text{1 H, 1 Cl}\end{array}$$ Sodium and potassium are atoms and not molecules.

However, oxygen gas $\left(O_2\right)$, ammonia $\left(N{H}_3\right)$, water $\left(H_{2}O\right)$ and hydrochloric acid $\left(HCl\right)$ are molecules as they are formed by the combination of more than one atoms.