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Topic: Xenon, Radon & Ununoctium - odd electron arrangements  (Read 2981 times)

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Offline memoguy

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Xenon, Radon & Ununoctium - odd electron arrangements
« on: July 21, 2012, 10:08:24 PM »
Hi!
I have just started chem at school and have a couple of questions for the bright minds over here on the forums.

1)
With the Nobel gasses, continually i see on the internet that the reason they are inert is due to the outer shell being full. But i don't see how this is true. I was taught that the shells have the following maximum capacities:
 2,8,18,32,50,72

So Helium & Neon are both at maximum capacity (with 2 and 2,8) but argon, Krypton, Xenon, Radon and Ununoctium are all not. They all have 8 electrons on the outer shell but these shells are above the second energy level maximum. Hmm, i don't think i articulated that very well. Let me try again:

if the maximums are:
2,8,18,32,50,72

Helium:
2
makes sense

Neon:
2,8
makes sense

Argon:
2,8,8
WOW! Why is the final layer an 8? For the outer layer to be at max capacity should it not be 18?

Krypton:
2,8,18,8
WOW! Why is the final layer an 8? For the outer layer to be at max capacity should it not be 32?

so i think you get my point there. Where is the final layer less than the maximum capacity despite a bunch of resources saying that Nobel gasses are inert due to the outer layer being at maximum capacity.


2)

I was told that the electrons flow on from layer to layer. So if there was 10 electrons then layer 1 fills to two, layer 2 fills to 8. That makes sense for Helium, Neon, Argon & Krypton. But then we get to Xenon where the shells go:
2,8,18, 18, 8

WOW! Why didn't layer 4 fill to 32 rather than 18, so the electron arrangement would be:
2,8,18,26

This confusion applies to Xenon, Radon and Ununoctium!


I thought i was getting the hang of chem but now it seems that these elements simply break the laws!

I would be so pleased if someone could give me a hand here.

Offline Dan

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Re: Xenon, Radon & Ununoctium - odd electron arrangements
« Reply #1 on: July 22, 2012, 03:06:53 AM »
You are using a highly simplified model for electronic structure, which is why it's not working. You will have to read about s, p, d, anf f subshells to understand the order of filling.

Read around the subjects of electronic configuration and the aufbau principle. For example: http://en.wikipedia.org/wiki/Electron_configuration
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