Noble gases, electron shell, how is it full?

I've heard for years that the outer electron shell of noble gases are full. Thus they are inert. This is true, therefore something is flawed about my understanding of electron shells and how they are filled. The sources below give a good summary of how electron shells and their sub-orbitals are filled. All the noble gases have 8 valence electrons.

First lets look at an element that I understand, Neon. The first suborbital fills with 2 electrons, and the 2nd shell with its "s" and "p" suborbitals can fill and have 8 valence electrons. And wouldn't you know that this is exactly what Neon does, so that makes sense. Now I look at Argon. It has an atomic number of 18. So the 1st shell uses 2 electrons, the 2nd shell uses 8. That leaves 8 electrons for the 3rd shell. The "s" and "p" suborbitals of the 3rd shell are filled leaving the "d" suborbital completely empty. That suborbital can hold another 10 electrons!

http://www.chemtube3d.com/A%20Level%20orbitals.htm

http://www.freewebs.com/ryanbchemistry/Images/Elec...