Rutherford's $\alpha$-particle scattering experiment is related to the size of the ..........

The radius of an atom is about

Which of the following statements is correct about the cathode rays?
$1$. These rays start from anode and move towards cathode.
$2$. They are visible with human eye.
$3$. In presence of electric and magnetic fields,they behave like positively charged particles.
$4$. Their characteristic does not depend on the nature of material at electrode.

The discovery of ......... was made through Rutherford's scattering experiment.

The minimum real charge on any particle which can exist is

Who discovered the neutron?