$A$ particle having almost zero mass and exactly zero charge is

Explain the types of atoms by illustrating with examples.

The radius of a Germanium $(Ge)$ nucleus is twice the radius of a $^9_4Be$ nucleus. The number of nucleons in $Ge$ is ......

In the nuclear reaction $X(n, \alpha) _3^7Li$,what is $X$?

The particle that possesses half-integral spin is:

The unit of length convenient on the nuclear scale is a fermi: $1 \; f = 10^{-15} \; m$. Nuclear sizes obey roughly the following empirical relation: $r = r_{0} A^{1/3}$,where $r$ is the radius of the nucleus,$A$ is its mass number,and $r_{0}$ is a constant equal to about $1.2 \; f$. Show that the rule implies that nuclear mass density is nearly constant for different nuclei. Estimate the mass density of a sodium nucleus.