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Topic: Why 4s e-(s) of transition metals is/are counted as 3d e-  (Read 9000 times)

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Offline Winga

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Why 4s e-(s) of transition metals is/are counted as 3d e-
« on: November 07, 2004, 12:24:36 PM »
Why 4s electron(s) of 3d transition metals is/are counted as 3d orbitals's when the metal forming a complex with the ligands?

Offline Mitch

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Re:Why 4s e-(s) of transition metals is/are counted as 3d e-
« Reply #1 on: November 07, 2004, 06:01:48 PM »
give an example
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Offline Winga

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Re:Why 4s e-(s) of transition metals is/are counted as 3d e-
« Reply #2 on: November 08, 2004, 05:36:10 AM »
For example,

e- configuration:
Ni: [Ar] 3d8 4s2

For the complex Ni(CO)4, Ni is said to be having 10 d-electrons, why?

Offline maxyoung

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Re:Why 4s e-(s) of transition metals is/are counted as 3d e-
« Reply #3 on: November 08, 2004, 07:53:50 AM »
the metal center is sp3 hybridized. The 4s orbital now is occupied by the ligands.  All the 10 e-s of the metal center now will occupy the d orbitals.

Also can see from the MO diagram. All the bonding orbitals are filled with electrons from the ligands. Electrons from the metal center will occupy the t2 and e* orbitals before they occupy the antibonding orbitals. So the ten electrons all willl be counted as d electrons in the complex.

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Re:Why 4s e-(s) of transition metals is/are counted as 3d e-
« Reply #4 on: November 08, 2004, 09:01:33 AM »
Can we use stability approach to explain it?

For example, e- in 3d-orbital is more stable than that in 4s-orbital when the complex is formed.

Offline Mitch

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Re:Why 4s e-(s) of transition metals is/are counted as 3d e-
« Reply #5 on: November 09, 2004, 05:04:10 PM »
The reason is not straight forward you have to look at a molecular orbital diagram. What they have taught you is how to count a theoritical construct which they call "d-electron count" using electrons from d and s. The term d-electron count is useful because it describes how many electrons sit on their butt neither bonding nor going antibonding(depending of crystal field splitting--but ignore for now) and just sit in 3 d-orbitals of t2g symmetry.
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