The decay of a proton to neutron is :

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason $R$. Assertion A : The nuclear density of nuclides ${ }_5^{10} B ,{ }_3^6 Li ,{ }_{26}^{56} Fe ,{ }_{10}^{20} Ne$ and ${ }_{83}^{209} Bi$ can be arranged as $\rho_{ Bi }^{ N }>\rho_{ Fe }^{ N }>\rho_{ Ne }^{ N }>\rho_{ B }^{ N }>\rho_{ Li }^{ N }$.

Reason $R$ : The radius $R$ of nucleus is related to its mass number $A$ as $R=R_0 A^{1 / 3}$, where $R_0$ is a constant.

In the light of the above statement, choose the correct answer from the options given below :

$STATEMENT-1$: The plot of atomic number ( $\mathrm{y}$-axis) versus number of neutrons ( $\mathrm{x}$-axis) for stable nuclei shows a curvature towards $x$-axis from the line of $45^{\circ}$ slope as the atomic number is increased. and  $STATEMENT-2$: Proton-proton electrostatic repulsions begin to overcome attractive forces involving protons and neutrons and neutrons in heavier nuclides.

The mass number of a nucleus is equal to the number of

The radius of germanium $(Ge)$ nuclide is measured to be twice the radius of ${}_4^9Be$ . The number of nucleons in $Ge$ are