An unknown nucleus has a nuclear density of $2.29 \times 10^{17} \text{ kg/m}^3$ and mass of $19.926 \times 10^{-27} \text{ kg}$. Its mass number $A$ is approximately: (Take $R_0 = 1.2 \times 10^{-15} \text{ m}$,$4\pi = 12.56$)

$A$ reaction between a proton and $_8^{18}O$ that produces $_9^{18}F$ must also liberate:

Assertion: Neutrons penetrate matter more readily as compared to protons.
Reason: Neutrons are slightly more massive than protons.

For a nucleus to be stable,the correct relation between neutron number $N$ and proton number $Z$ is

The neutron was discovered by

The unit of length convenient on the nuclear scale is a fermi: $1 \; f = 10^{-15} \; m$. Nuclear sizes obey roughly the following empirical relation: $r = r_{0} A^{1/3}$,where $r$ is the radius of the nucleus,$A$ is its mass number,and $r_{0}$ is a constant equal to about $1.2 \; f$. Show that the rule implies that nuclear mass density is nearly constant for different nuclei. Estimate the mass density of a sodium nucleus.