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Topic: Anyone know why? {Atomic orbitals}  (Read 5122 times)

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Offline Nescafe

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Anyone know why? {Atomic orbitals}
« on: June 23, 2012, 10:04:29 AM »
The atomic orbital of more electronegative atoms such as oxygen is lower in energy than those of carbon for example?
« Last Edit: June 23, 2012, 10:24:26 AM by Arkcon »
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Offline Dan

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Re: Anyone know why?
« Reply #1 on: June 23, 2012, 10:15:44 AM »
Lower in energy means more stable. What would you say stabilises electrons?
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Offline Nescafe

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Re: Anyone know why?
« Reply #2 on: June 23, 2012, 10:16:39 AM »
Quote from: Dan on June 23, 2012, 10:15:44 AM
Lower in energy means more stable. What would you say stabilises electrons?

Electron withdrawingnessness :P of the oxygen?
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Offline Dan

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Re: Anyone know why?
« Reply #3 on: June 23, 2012, 10:18:17 AM »
Why is oxygen electron withdrawing?
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Offline Nescafe

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Re: Anyone know why?
« Reply #4 on: June 23, 2012, 10:22:22 AM »
Quote from: Dan on June 23, 2012, 10:18:17 AM
Why is oxygen electron withdrawing?

Because it is electron hungry (electronegative)? Pulls the electrons towards itself and keeps them nice and warm like a mother embracing her kids :)
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Offline Dan

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Re: Anyone know why? {Atomic orbitals}
« Reply #5 on: June 23, 2012, 10:41:30 AM »
But why? What is attracting the electrons? Why are they held tightly?
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Offline Nescafe

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Re: Anyone know why? {Atomic orbitals}
« Reply #6 on: June 23, 2012, 12:59:52 PM »
The nucleus, the large nuclear charge of the oxygen atom results in the electrons experiencing a great deal of net positive charge imposed by the nucleus of the oxygen atom. Correct me if I'm wrong please,

Nescafé.
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Offline Dan

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Re: Anyone know why? {Atomic orbitals}
« Reply #7 on: June 23, 2012, 01:41:21 PM »
You're absolutely right. So how does that fit in when it comes to answering your original question?
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Offline Nescafe

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Re: Anyone know why? {Atomic orbitals}
« Reply #8 on: June 23, 2012, 03:16:56 PM »
Electrons are negatively charged, the more they experience the positive influence of the nuclear charge the more stablized they will be. After all positive and negative attract ( Paula Abdul song :P ). Since electrons of oxygen experience the nuclear charge of the oxygen atom quite distinctively, they are stablized and therefore the atomic orbitals in which they reside in  are of lower energy (more stable).
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Offline Dan

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Re: Anyone know why? {Atomic orbitals}
« Reply #9 on: June 23, 2012, 09:42:26 PM »
Sounds good to me, well done.
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Offline cheese (MSW)

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Re: Anyone know why? {Atomic orbitals}
« Reply #10 on: June 23, 2012, 11:00:56 PM »
I am afraid Dan is not correct. C 6+ nucleus, 6 e⁻ Zeff =  3.25 (Slater) 3.14 (Clementi)
O 8+ nucleus 8 e⁻ Zeff = 4.55 (Slater) 4.45 (Clementi) E α -Zeff/r
It is the effective nuclear charge (which affects the radius) that is important.
Look through my recent posts for a question that has effective nuclear charge in the title.
Basically valence e⁻ do a poor job of screening the nuclear charge from each other.
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Offline Dan

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Re: Anyone know why? {Atomic orbitals}
« Reply #11 on: June 24, 2012, 07:00:17 AM »
Where did I say it was not caused by effective nuclear charge?

Nescafe deduced that if the electrons experienced greater nuclear charge, they would be lower in energy. The charge experienced by the electron is the effective nuclear charge. It's the same argument you are using.
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Offline cheese (MSW)

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Re: Anyone know why? {Atomic orbitals}
« Reply #12 on: June 26, 2012, 08:52:59 PM »
Not so Dan: Let's say that each of the other e⁻ screens a valence e⁻ equivalent to -1.
Then the Zeff on C would be 6-5 = 1+ and on O 8-5 = 1+.
And it can't of course be directly proportional to Z the nuclear charge.
Zeff for Na is 2.20 (Slater) 2.51 (Clementi).  It is all explained by the SWE.
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