Question

The number of atoms in a molecule of the elementary substance is called:

• A. Atomic number
• B. Avogadro number
• C. Atomic mass scale
• D. Atomicity

Answer 1

The correct option is D

Atomicity

Explanation for correct option:

Option D: Atomicity:

The number of atoms in a molecule of the elementary substance is called atomicity.

Example:

• One molecule of Carbon dioxide $\mathbf{\left(}{\mathbf{CO}}_{\mathbf{2}}\mathbf{\right)}$, contains one atom of carbon $\mathbf{\left(}\mathbf{C}\mathbf{\right)}$ and two atoms of oxygen $\mathbf{\left(}\mathbf{O}\mathbf{\right)}$.
• Thus, the total number of atoms or atomicity of Carbon dioxide is $3$.

Explanation for Incorrect options:

Option A: Atomic number:

Atomic number refers to the number of protons in an element.

Option B: Avogadro number:

Avogadro number refers to the number of units in a mole of a substance.

Option C: Atomic mass scale:

The atomic mass scale refers to the mass of one atom of $\mathrm{C}-12$.

Thus, option (D) is the correct option. The number of atoms in a molecule of the elementary substance is called atomicity.