In a helium nucleus,there are

In the nuclear reaction $_2He^4 + _zX^A \to _{z+2}Y^{A+3} + A$,$A$ denotes:

The radius of a Germanium $(Ge)$ nucleus is twice the radius of a $^9_4Be$ nucleus. The number of nucleons in $Ge$ is ......

Which of the following pairs is an isobar?

The radius of the nucleus of silver (atomic number $Z = 47$) is $3.4 \times 10^{-14} \ m$. Calculate the electric potential on the surface of the nucleus. (Given: $e = 1.6 \times 10^{-19} \ C$,$\frac{1}{4\pi\epsilon_0} = 9 \times 10^9 \ N \ m^2/C^2$)

The three stable isotopes of neon: $_{10}^{20}Ne$,$_{10}^{21}Ne$,and $_{10}^{22}Ne$ have respective abundances of $90.51\%$,$0.27\%$,and $9.22\%$. The atomic masses of the three isotopes are $19.99\;u$,$20.99\;u$,and $21.99\;u$ respectively. Obtain the average atomic mass of neon. (in $;u$)