Starting from radium,the radioactive disintegration process terminates when the following is obtained:

The atomic mass of lead is $208$ and atomic number is $82$. The atomic mass of bismuth is $209$ and atomic number is $83$. The ratio of $n/p$ in the atom is

The positron is

The isotopic mass of ${}_{3}^{7}Li$ is $7.016005 \ u$ and those of the $H$ atom and neutron are respectively $1.007825 \ u$ and $1.008665 \ u$. Then,the binding energy of the ${}_{3}^{7}Li$ nucleus is: (in $MeV$)

If the mass defect of a nuclide is $3.32 \times 10^{-26} \ g$,its binding energy in $MeV$ is:

The order of density in the nucleus is: