Question

Write the increasing order of sizes of Na, Na+
,F, F-.

Answer 1

Size of the elements decreases as we go left to right in a period this happens due to the addition of electrons inside the same shell which leads to increase in the attraction between the nucleus and the outermost electrons

AND it increases as we go down the grp due to increase in the no of shells

When an electron is removed(+) from the outermost shell the no of electrons in the outermost shell decreases this leads to increase in the attraction between the electrons and the nucleus thus reducing it's size

When an electron is added (-) in the outermost shell the electrons of the other shells start repelling each other and thus the atom increases it's size

Hence the order is

F->Na >F>Na+

I hope this helps (≧▽≦)