The ratio of the masses of a proton and an electron is:

Calculate the mass of $1$ mole of neutrons in $kg$. $\left( m_n = 1.675 \times 10^{-27} \ kg \right)$

The nucleus of an atom can be assumed to be spherical. The radius of the nucleus of mass number $A$ is given by $1.25 \times 10^{-13} \times A^{1/3} \ cm$. The radius of the atom is $1 \ \mathring{A}$. If the mass number is $64$,then the fraction of the atomic volume that is occupied by the nucleus is:

$A$ certain particle carries $2.5 \times 10^{-16} \, C$ of static electric charge. Calculate the number of electrons present in it.

The ratio of specific charge of a proton and an $\alpha$-particle is

Who discovered the proton and the neutron?