Deuterium is an isotope of hydrogen and is represented by ${}_1^2\text{H}$. How many deuterium atoms are present in heavy water?

The correct option is B

2

Deuterium is an isotope of hydrogen. It has only one electron. The chemical formula of heavy water is ${\text{D}}_2\text{O}$. Thus, there are two deuterium atoms in a molecule of a heavy water.