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Topic: Electronic configuration of Carbon  (Read 8322 times)

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Offline photophobic

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Electronic configuration of Carbon
« on: September 13, 2011, 05:58:12 AM »
We all know that carbon shows the configuration 1s2- 2s2- 2p2
But, since half-filled and fully filled orbitals are more stable, why doesn't it show the configuration 1s2- 2s1- 2p3 ?
Why doesn't the 2s orbital give 1 electron to 2p, as in the case of Chromium, where one electron goes from 3d to 4s, in order to make both orbitals half-filled(and hence more stable)?

Offline Borek

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Re: Electronic configuration of Carbon
« Reply #1 on: September 13, 2011, 07:37:43 AM »
It is all in the energy - and rules of thumb give only some pointers, not the final answers. These require either precise measurements, or precise calculations, and final results are often not what we expect.

Besides, I have no idea what is the electron configuration of the carbon. In diamond it is hybridized to sp3, in graphite it is sp2 - neither qualifies as s2p2.
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Offline fledarmus

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Re: Electronic configuration of Carbon
« Reply #2 on: September 13, 2011, 07:57:01 AM »
We all know that carbon shows the configuration 1s2- 2s2- 2p2
But, since half-filled and fully filled orbitals are more stable, why doesn't it show the configuration 1s2- 2s1- 2p3 ?
Why doesn't the 2s orbital give 1 electron to 2p, as in the case of Chromium, where one electron goes from 3d to 4s, in order to make both orbitals half-filled(and hence more stable)?

I think you got that backwards - in Cr, one electron goes from 4s to 3d - the 4s orbitals are actually lower in energy than the 3d ones, and get filled first. But they are close enough in energy that the additional energy savings in having a half-filled orbital is sufficient to overcome the gap between 4s and 3d.

The 2s and 2p orbitals are further apart in energy, and the energy savings of a half-filled 2p orbital isn't enough to overcome the energy required to lift an electron from 2s to 2p.

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