which has the lowest Ionization ENERGY? Cl-(anion), Ar, K+ (Cation)?

the pattern in the periodic table will give us : Ar>Cl>K but because Cl is anion so it would have the lowest IE, we have

Ar>K>Cl

In this case all the ions have same e- configuration but different values of atomic no.

As chloride has least positive charge in its nucleus so its force on the electrons is minimum. Hence its IE will be minimum

cl -