Question

Which amongst the following gases exist as a triatomic molecule?

• A. Nitrogen
• B. Carbon dioxide
• C. Carbon monoxide
• D. Helium

Answer 1

The correct option is B Carbon dioxide

Atomicity is defined as the number of atoms in a molecule.
$$\begin{array}{cccc}\text{Gas}& \text{Molecule}& \text{Constituent atoms}& \text{Atomicity}\\ \text{Nitrogen}& N_2& \text{2 N}& \text{2}\\ \text{Carbon dioxide}& C{O}_2& \text{1 C, 2 O}& \text{3}\\ \text{Carbon monoxide}& CO& \text{1 C, 1 O}& \text{2}\\ \text{Helium}& He& \text{1 He}& \text{1}\end{array}$$
Hence, carbon dioxide is a triatomic molecule.