What are the charge,mass,and charge-to-mass ratio of an electron?

The size of the nucleus is measured in

The $(e/m)$ ratio for positive rays in comparison to cathode rays is

Fill in the blanks given below:
$(i)$ The picture on the television screen is visible due to the presence of .......... on the screen.
$(ii)$ In the presence of electric and magnetic fields,cathode rays are known as .......... .
$(iii)$ The measurement of the $e/m_e$ ratio for electrons was performed by the scientist .......... .
$(iv)$ In a cathode ray tube,the greater the magnitude of the charge on the particles,the .......... the deflection of the particles.

The mass to charge ratio $(m/e)$ of a cation is $1.5 \times 10^{-8} \ kg/C$. What is the mass of the ion?

The volume of the atomic nucleus is $......$ of the volume of the atom.