# Atomic radius of K+ vs. Argon

1. Nov 21, 2012

### assaftolko

How is it that these two have the same electron level array (1s^22s^22p^63s^23p^6), but K+ has bigger radius than Ar?
K+ has one more proton in its nuclei than Ar, so I would expect that if both have the same electron configuration - the one with more protons in its nuclei would have the smaller radius since the electric force between its nuclei and its electrons is bigger, hence pulling the two closer together...

2. Nov 21, 2012

### AGNuke

Never heard K+ being larger than Ar. But K (atom) is certainly larger than Ar.

3. Nov 25, 2012

### epenguin

I think this is a good question - you may even have opened a can of little maggots, and I will give my fairly amateur answer hoping for greater expertise to come along.

Firstly be reassured that the lines of your explanation are right and followed by all I have been able to read.

About the anomaly you do not give figures and you do not tell us where your ‘fact’ comes from.
This reference