The $\alpha$-particle is identical with

$A$ neutral atom (Atomic number $Z > 1$) consists of:

The number of electrons in the nucleus of $^{12}C$ is

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

Which of the following particles cannot be accelerated by an electric or magnetic field?

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.