What happens to ionic size across a period?

Thus, why?

We know that nuclear charge is very imperfectly shielded by partially filled electronic shells; as a result, atomic size decreases from left to right throughout the Period.

Though atoms on the right hand side of the Periodic Tables are oxidizing species, electron acceptors, and therefore get reduced, atoms on the left hand side of the Tables are METALS, which are reducing species (and therefore get oxidized), which is why ionic size should increase across the Period from left to right. The ionic size of fluoride and oxide anions should be much greater than their parent atoms because they have extra electronic charge to accommodate.

We can legitimately overlook the chemistry of the noble gases in these reactivity discussions because they have a whole electronic shell.

Ionic size decreases across a period due to increasing nuclear charge, which attracts the electrons more strongly, resulting in a smaller atomic radius.