Which Atom Has a Larger Atomic Radius: K+ or Ar?

[rdgt3000]

which atom has a larger atomic radius: K+ or Ar ?

 

[mrjeffy321]

Both have the same number of electrons, but think about the number of protons in the nucleus of the K+ ion and in the Argon atom. How will the number of protons affect the atomic (or ionic) radius? Think of the general periodic trend of atomic radii when the outermost shell is the same but atomic number is increasing.