Determining size of atom

[juliaddc]

I saw this problem in one of the Step Up worksheets:
"Arrange in order of decreasing size: Na+, Ne, F-"
My question is, how can they be different sizes if they end up being in the same spot in the periodic table.

[Valeria Perez 3J]

If they end up with the same electron configuration, the next step is to look at the numver of protons. The higher the number of protons, the more positive pull there will be on the electrons, leading to a smaller ion, and vice versa. Hope that helps!