Electron accountancy

| Subject classification: this is a chemistry resource.

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| Type classification: this is a lesson resource.

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## Aims

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This Lesson will cover:

* Revision of electron counting methods
* The Covalent Bond Classification as an alternative method
* Simple classes of ligand and bond ambiguities
* Curly arrow conventions in complexes
* Composite ligands
* Formal oxidation state and the d-electron count
* Coordination number and ambiguities

## Classes of ligand

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### L ligands (2e donors)

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* PR3, N2, C2H4, CO, H2, C2H2
* observed as neutral

### X ligands (1e donors)

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* H, halides, R (alkyl), Ar (aryl), COR (acyl), OR (alkoxides), NR2
* observed as anions

## Composite ligands

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## Electron counting

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The number of electrons donated by the metal = its group number.

Valence Number (VN)

VN = number of X ligands + charge on complex

Coordination Number (CN)

CN = number of atoms bonded to the metal CN = number of electron pairs added to the metal CN = number of ligands bonded to the metal

Ligand Bond Number (LBN)

LBN = sum of L and X ligands