Electron accountancy

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Nuvola apps edu science.svg Subject classification: this is a chemistry resource.
Nuvola apps edu miscellaneous.svg Type classification: this is a lesson resource.

Aims[edit]

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[edit]

L ligands (2e donors)[edit]

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

X ligands (1e donors)[edit]

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


Composite ligands[edit]

Electron counting[edit]

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