What is the difference in atomic radius between ions?

Question

If i have O and O^2-, which has a larger atomic radius, and why, is it shielding, energy level, or nuclear charge, i think shielding and nuclear chrage, but im really not sure

another example Ca, or Ca^2+

Answer 1

o^2- has same radius for the simple structure.
As both the octet stucture and the non ionoc state are in the same state 9 valence electrons)
and
ca is bigger as it loses one shell after losing 2 electrons.
it is a nuclear charge bec. it has a charge

Answer 2

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