Most p-block elements have both positive and negative oxidation states.
The elemental form (oxidation state 0) of these elements can hence act as either an oxidant or a reductant as seen in the Hydrogen module.
The elemental form (and other intermediate oxidation states) may react by autooxidation-reduction as seen in the examples below.
- The maximum is the last digit of the group number (except for oxygen and fluorine for which the maximum is 0).
- The minimum is the Group Number - 18.
The elemental form (oxidation state 0) of these elements can hence act as either an oxidant or a reductant as seen in the Hydrogen module.
The elemental form (and other intermediate oxidation states) may react by autooxidation-reduction as seen in the examples below.
In these reactions an atom in an intermediate oxidation state acts as both the oxidant and the reductant.
The conditions under which autooxidation-reduction takes place varies from system to system.
The conditions under which autooxidation-reduction takes place varies from system to system.
| 3NO2(g) | + | H2O |  | 2HNO3(l) | + | NO(g)3 |
| N(+4) | N(+5) | N(+2) |
| 4KClO3(s) | | 3KClO4(s) | + | KCl(s) |
| Cl(+5) | Cl(+7) | Cl(-1) |