Question

Which of the following pairs are isotopes?

• A. Ice and steam
• B. Hydrogen and Deuterium
• C. Nitric oxide and Nitrogen dioxide
• D. Oxygen and Ozone

Answer 1

The correct option is B

Hydrogen and Deuterium

Explanation for correct option

(B)Hydrogen and Deuterium

Isotopes:

• Atoms with identical atomic numbers but different mass numbers are known as Isotopes.
• Hydrogen $\left({\mathrm{H}}_1^1\right)$and deuterium$\left({\mathrm{H}}_1^2\right)$ have the same atomic number but varying mass numbers, making them isotopes of each other.

Explanation for incorrect option

Option (A)

Ice and steam are not isotopes, but instead two separate types of water with different physical states of matter.

Option (C)

In Nitric oxide $\left(\mathrm{NO}\right)$and nitrogen dioxide$\left({\mathrm{NO}}_2\right)$ ,the chemical formulae of each are different, hence they cannot be isotopes.

Option (D)

There are two atoms of oxygen in oxygen$\left({\mathrm{O}}_2\right)$ and three atoms of oxygen in ozone$\left({\mathrm{O}}_3\right)$, they are not isotopes of each other.

Hence, option (A), (C), (D) are incorrect.

Hence, option (B) is correct. Hydrogen and Deuterium are pairs of isotopes.