$^{22}Ne$ nucleus after absorbing energy decays into two $\alpha$-particles and an unknown nucleus. The unknown nucleus is

If the radius of a nucleus with mass number $125$ is $1.5 \text{ fermi}$, then the radius of a nucleus with mass number $64$ is: (in $\text{ fermi}$)

How many neutrons are more than protons in the ${ }_{92}^{235} U$ nucleus?

Which of the following pairs is an isobar?

$(a)$ Two stable isotopes of lithium $_{3}^{6} Li$ and $_{3}^{7} Li$ have respective abundances of $7.5 \%$ and $92.5 \%$. These isotopes have masses $6.01512 \; u$ and $7.01600 \; u$,respectively. Find the atomic mass of lithium.
$(b)$ Boron has two stable isotopes,$_{5}^{10} B$ and $_{5}^{11} B$. Their respective masses are $10.01294 \; u$ and $11.00931 \; u$,and the atomic mass of boron is $10.811 \; u$. Find the abundances of $_{5}^{10} B$ and $_{5}^{11} B$.

The radius of a nucleus with atomic number $Z = 50$ is $9 \times 10^{-13} \ m$. The electric potential at its surface is: