How do you compare sizes of cations to anions? An example would be: Arrange in order of decreasing size. Na+, Rb+, O3-, F-

Question

aaronq · Answer

how many protons does each have? how many electrons?

$Na^+$ has 11 protons, 10 electrons
$F^-$ has 9 protons, 10 electrons

the valence (outermost) electrons on the sodium ion "experience" a greater attraction because there are more protons, these are drawn closer shrink the radius of the ion, in comparison to the fluoride ion (where there are less protons but the same amount of electrons). |dw:1382497129805:dw|

joannablackwelder · Answer

I have a table that shows that Na+ is also smaller than O2-.

aaronq · Answer

oh nice. I wouldn't be sure to assert that by just doing comparisons like these, you'd have to calculate $Z_{eff}$.