Argon have three neutron rings 2,8,8 and has fullfilled its rings.
Krypton have four; 2,8,18(??),8 rings.

How come Krypton have eighteen electrons in its third ring, while
argon have eight, and is already full ?

How does the periodic system work according to this ? - the numbering of rings

as far as I know, a noble gas is an atom that has fullfilled its
el.rings. Which is why I find this third-ring kinda frustrating :)

with thanks

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Clarification of Question by vendel-ga on 12 Jul 2006 16:58 PDT

Argon have three electron rings 2,8,8 and has fullfilled its outer rings.
Krypton have four rings; 2,8,18(??),8 

How come Krypton have eighteen electrons in its third ring, while
argon have eight, and still is a noble gas if its outer ring can be
added further with electrons?

How does the periodic system work according to the numbering of rings?

as far as I know, a noble gas is an atom that has fullfilled its
outer electron ring. Which is why I find this third-ring argon/krypton
kinda frustrating :)

Thank You