The $\alpha$-particle is identical with

The mass of a proton is $... \ g$.

Neutrons are found in atoms of all elements except in

What are canal rays? Write their characteristics.

The radius of a nucleus with mass number $A$ is given by $1.25 \times 10^{-13} \times A^{1/3} \ cm$. If the radius of the atom is $1 \ \mathring{A}$ and the mass number is $64$,calculate the fraction of the volume occupied by the nucleus.

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