Question

An atom contains $22$ neutrons in its nucleus and $18$ electrons around it.

1. It contains _____ protons in its nucleus.
2. Its atomic number is _____ .
3. Its mass number is _____ .

Answer 1

1. Given, no. of neutrons = $22$ and no. of electrons = $18$
2. Since $\mathrm{no}.\mathrm{of}\mathrm{protons}=\mathrm{no}.\mathrm{of}\mathrm{electrons}$, Therefore, no. of protons = $18$
3. Since$\mathrm{atomic}\mathrm{number}\mathrm{of}\mathrm{an}\mathrm{atom}=\mathrm{no}.\mathrm{of}\mathrm{protons},$ Therefore, atomic number = $18$
4. $\mathrm{Mass}\mathrm{number}=\mathrm{no}.\mathrm{of}\mathrm{protons}+\mathrm{no}.\mathrm{of}\mathrm{electrons}$= $18+22=40$

Therefore,

1. It contains $18$ protons in its nucleus.
2. Its atomic number is $18$.
3. Its mass number is $40$.