Q.
The radius of $R$ of a nucleus of mass number A can be estimated by the formula $R =\left(1.3 \times 10^{-15}\right) A ^{1 / 3} m$ It follows that the mass density of a nucleus is of the order of:
$\left( M _{\text {prot. }} \cong M _{\text {neut. }} \simeq 1.67 \times 10^{-27} kg \right)$
Solution: