Who discovered the neutron?

Nuclear reactions are given as:
$(i) \, \square (n, p) {_{15}}P^{32}$
$(ii) \, \square (p, \alpha) {_{8}}O^{16}$
$(iii) \, {_{7}}N^{14} (\square, p) {_{6}}C^{14}$
The missing particles or nuclides (in box $\square$) in these reactions are respectively:

Specify the mass of a proton in kilograms and in the $u$ (atomic mass unit).

The mass number of a nucleus having a radius equal to half of the radius of a nucleus with mass number $192$ is:

In the nuclear reaction: $X(n, \alpha) {_3Li^7}$,the term $X$ will be

Calculate the height of the potential barrier for a head-on collision of two deuterons. (Radius of deuteron is $2$ fm).