Editing Electron counting (section)

==Electrons donated by common fragments==
{| class="wikitable"
|-
! Ligand !! Electrons contributed<br/>(neutral counting) !! Electrons contributed<br/>(ionic counting) !! Ionic equivalent
|-
| [[Halide|X]] || 1 || 2 ||X<sup>−</sup>; X = F, Cl, Br, I
|-
| [[Hydride|H]] || 1 || 2 ||H<sup>−</sup>
|-
| [[Hydrogen|H]] || 1 || 0 ||H<sup>+</sup>
|-
| [[Oxide|O]] || 2 || 4 ||O<sup>2−</sup>
|-
| [[Nitride|N]] || 3 || 6 ||N<sup>3−</sup>
|-
|[[Carbonyl ligand|CO]]
|2
|2
|CO
|-
| [[Amine|NR<sub>3</sub>]] || 2 || 2 ||NR<sub>3</sub>; R = H, alkyl, aryl
|-
| [[Alkylidene|CR<sub>2</sub>]] || 2 || 4 ||{{chem2|CR2(2−)}}
|-
| [[Ethylene]] || 2 || 2 ||C<sub>2</sub>H<sub>4</sub>
|-
| [[Cyclopentadienyl complex|cyclopentadienyl]] || 5 || 6 ||{{chem2|C5H5-}}
|-
| [[benzene]] || 6 || 6 ||C<sub>6</sub>H<sub>6</sub>
|}

==="Special cases"===
The numbers of electrons "donated" by some ligands depends on the geometry of the metal-ligand ensemble.  An example of this complication is the M–[[Nitrosyl|NO]] entity. When this grouping is linear, the NO ligand is considered to be a three-electron ligand.  When the M–NO subunit is strongly bent at N, the NO is treated as a pseudohalide and is thus a one electron (in the neutral counting approach).  The situation is not very different from the ''η''<sup>3</sup> versus the ''η''<sup>1</sup> allyl.  Another unusual ligand from the electron counting perspective is [[sulfur dioxide]]. 
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