Which particle cannot be accelerated?

Which of the following particles is represented by the symbol $\alpha$?

The average distance of an electron in an atom from its nucleus is of the order of:

Neutrons are found in atoms of all elements except in

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.

The mass of a neutron is nearly