Problem $2$:

A Lithium nucleus $-$ which is made of $2$ protons $(p)$ and $1$ neutron $(n)-$ is located

between the plates of a parallel$-$plate capacitor as shown.

$[$a$]$ Calculate the mass and charge of this nucleus

$[$b$]$ Draw the electric force acting on the nucleus

$[$c$]$ How large should this force be to exactly balance the weight of the nucleus

so that the nucleus remains stationary?