Which is the correct statement about a proton?

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.

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

$A$ particle having the same charge and $200$ times greater mass than that of an electron is:

Calculate the ratio of the diameter of an atom to the diameter of its nucleus.

The positive charge of an atom is