b
\(F ^{-}\)is the biggest in size. As we know that when we go right in a period atoms become smaller in size because no of orbit is not changing ,no of proton is increasing ,no of electron is increasing so that attraction between protons and electrons will increase so the size will decrease.

In \(F ^{-}\), no of electrons is more than no of protons so that protons can 't attract electrons very heavily. In \(Na ^{+}\)no of electrons is less than no of protons so that protons will attract electrons more heavily thus its size will decrease. Ne has the same no of electrons and protons. \(F ^{-}\,> \,Ne \,> \,Na ^{+}\) will be the order.