[TrpnBils]

I've seen two different things here and I need to get it cleared up... does the third electron shell hold a maximum of 8 or 18 electrons? Here's why I'm asking:

Argon is stable. Everything I can track down says what I had originally thought.... it's stable because its outer shell is full. This would indicate that the third shell held a maximum of 8 electrons.

BUT if you look at the electron configuration model the third shell's profile looks like this: 3s²3p⁶3d¹⁰, which seems to support the idea that the whole shell can hold up to 18 electrons. But if that's the case, why isn't Nickel (which fills the entire 3d¹⁰ part) stable instead of Argon?

I thought I was always taught that you could determine how many electron rings you'd see in a Bohr model diagram by look at the row number in which it would be found on the periodic table. In other words, Hydrogen and Helium only have one ring (Row #1), everything Lithium through Neon would have two rings (Row #2), and so on. If that's the case, then it would support the idea that the maximum of 18 electrons wouldn't start until you go to potassium in the 4th row.

What's the deal here???

[Borek]

http://en.wikipedia.org/wiki/Aufbau_principle

[TrpnBils]

Not to sound like a jerk, but I can look things up on Wikipedia too.... I was hoping for something in plain English.

Anything else?

[fledarmus]

Not to sound like a jerk...

Didn't work.

However, if you will read that article on the Aufbau principle, you will find that what you had originally thought was not, in fact true. Although the third shell can hold 18 electrons, part of the fourth shell gets filled before the third shell does, and part of the sixth shell is filled before the fourth shell does. The most stable elements are those which have 8 electrons in their outer shell.