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

The size of the nucleus is of the order of

Provide general information about the fundamental particles of an atom.

The radius of the nucleus is related to the mass number $A$ by

The volume of an atom is $10^5$ times the volume of its nucleus. If we consider the ratio of the radius of an atom to the radius of its nucleus,it is approximately $10^5$. Since volume $V = \frac{4}{3} \pi r^3$,the ratio of volumes is $(\frac{r_{atom}}{r_{nucleus}})^3 = (10^5)^3 = 10^{15}$. Therefore,the volume of an atom is $10^{15}$ times the volume of the nucleus. Choose the correct factor.

Who discovered the proton and the neutron?