Question

What is mass number of an element ? How is the mass number related to the protons and neutrons present in the nucleus of an atom ? Is it same as atomic number ?

Answer 1

MASS NUMBER

1. The mass of an atom is represented by mass number.
2. The mass number is defined as the sum of protons and neutrons in an atom of the element.
3. The mass number is related to the protons and neutrons present in the nucleus of an atom, by the following formula:
4. Mass number ($\mathrm{A}$) = $\mathit{N}\mathit{o}\mathit{.}\mathit{}\mathit{o}\mathit{f}\mathit{}\mathit{p}\mathit{r}\mathit{o}\mathit{t}\mathit{o}\mathit{n}\mathit{s}\mathit{}\mathit{\left(}\mathit{p}\mathit{\right)}\mathit{+}\mathit{}\mathit{N}\mathit{o}\mathit{.}\mathit{}\mathit{o}\mathit{f}\mathit{}\mathit{n}\mathit{e}\mathit{u}\mathit{t}\mathit{r}\mathit{o}\mathit{n}\mathit{s}\mathit{}\mathit{\left(}\mathit{n}\mathit{\right)}$.
5. ie ; $\mathrm{A}=\mathrm{p}+\mathrm{n}$
6. Mass number is not same as the atomic number.
7. Atomic number is equal to the number of protons, hence the mass number is not same as atomic number.