Overview of analysing redox properties

Most p-block elements have both positive and negative oxidation states.

  • 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.

3NO2(g) + H2O 2HNO3(l) + NO(g)3   4KClO3(s) 3KClO4(s) + KCl(s)
N(+4)       N(+5)   N(+2)   Cl(+5)   Cl(+7)   Cl(-1)