[jennielynn_1980]

I am not sure I have the right answer here.  I feel like I am missing a piece of the puzzle.  The question is:

Arrange the following ions in order of increasing radius:
Cl, S^2-, K, K⁺, O
Give an explaination of the postion of S^2- in relation to the atom or ion that comes just before and just after it.

So here is my answer:

The order is: O, Cl, S^2-, K⁺, K

For the second part of the question I think the answer is:
The electron configuration for Cl, S^2-, and K⁺ are all very similar.  K⁺ and S^2- both have the same electron configuration and Cl has one less electron in it's 3p shell.

Now what I can't figure out is this, if K⁺ and S^2- both have the same electron configuration, then why isn't K+ smaller because it has more protons which would increase the electrostatic force between the electrons and the protons, pulling the electron cloud closer to the nucleus.   According to what I looked up, K⁺ has a radius of 152 pm and S^2- has a radius of 103 pm.

[Neecze]

First question - dou you think that Cl, K and O are ions?

According to what I looked up, K+ has a radius of 152 pm and S2- has a radius of 103 pm.

But notice that sulphur has much more value of electronegativity than potassium. Because of weaker attraction of electrons K⁺ has bigger radius.

[jennielynn_1980]

Okay, thanks for pointing that out.  That helps