Rutherford's $\alpha$-particle scattering experiment proved that an atom has

The positron was discovered by

Who discovered the neutron?

The size of the nucleus is of the order of

In Millikan's experiment,static electric charge on the oil drops has been obtained by shining $X$-rays. If the static electric charge on the oil drop is $-1.282 \times 10^{-18} \ C,$ calculate the number of electrons present on it.

The nucleus of the atom consists of