Editing Oxidation state (section)

=== Nominal oxidation states ===
A nominal oxidation state is a general term with two different definitions:
* [[Electrochemistry|Electrochemical]] oxidation state<ref name="10.1515/pac-2013-0505" />{{rp|1060}} represents a molecule or ion in the [[Latimer diagram]] or [[Frost diagram]] for its redox-active element. An example is the Latimer diagram for [[sulfur]] at pH&nbsp;0 where the electrochemical oxidation state +2 for sulfur puts [[thiosulfate|{{chem|HS|2|O|3|−}}]] between S and [[sulfurous acid|H<sub>2</sub>SO<sub>3</sub>]]:

::[[File:16oxstate.svg|frameless|600px]]
* Systematic oxidation state is chosen from close alternatives as a pedagogical description. An example is the oxidation state of phosphorus in [[phosphorous acid|H<sub>3</sub>PO<sub>3</sub>]] (structurally [[diprotic]] HPO(OH)<sub>2</sub>) taken nominally as +3, while [[Electronegativity#Allen electronegativity|Allen electronegativities]] of [[phosphorus]] and [[hydrogen]] suggest +5 by a narrow margin that makes the two alternatives almost equivalent:
::[[File:17oxstate.svg|frameless|450px]]
:Both alternative oxidation numbers for phosphorus make chemical sense, depending on which chemical property or reaction is emphasized. By contrast, a calculated alternative, such as the average (+4) does not.