Which one of the following sets of ions represents the collection of isoelectronic species?
(Atomic numbers of F =9, Cl= 17,Na = 11, Mg=12,Al= 13,K= 19, Ca=20, Sc=21)
(a) K+, Ca2+, Sc3+, Cl- (b) Na+, Ca2+, Sc3+, F-
(c) K+, Cl-, Mg2+, Sc3+ (d) Na+, Mg2+,Al3+, Cl-
