Question

If the atomic mass of sodium is $23u$, what will be the atomic mass of sodium ion?

Answer 1

Atomic mass$=$ Number of neutrons $+$ Number of protons.

For $Na,N_n=12,N_p=11$

$23u=12+11$

For, $N{a}^{+},$ an electron is lost, but the atomic mass remains the same $\left(23u\right)$ as that of $Na.$