How can i find nuclear charge and overall charge while only knowing the atomic mumber, number of protons and electrons?

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.

the answer for sodium is 0.186

the answer for rubidium is 0.251