Question

How does the mass number of an atom help us to calculate the atomic mass of the element?

Answer 1

Mass number:

The mass number is defined as the sum of the number of electrons and the number of neutrons in the atom.

Atomic mass:

The mass of one atom of an element expressed in atomic mass unit is known as the atomic mass.

Mass number to calculate the atomic mass of the element:

1. The mass number gives the atomic mass of the element.
2. The mass of an atom is the mass of protons and neutrons in it.
3. This is because the mass of electrons is very less compared to the mass of protons and neutrons together.
4. thus, the mass of electrons is neglected.

Example:

1. Consider Carbon $\mathbf{\left(}\mathbf{C}\mathbf{\right)}$ atom having $6$ protons, $6$ neutrons and $6$ electrons.
2. Thus, the mass number of Carbon is $12$.
3. And the atomic mass of Carbon is $12\mathrm{u}$.