Oxidation State

Account for changes in the oxidation state of species in terms of their loss or gain of electrons



  • Oxidation state: A measure of a chemical species’ degree of oxidation.
  • Uncombined elements have an oxidation state of zero.
  • Simple ions have an oxidation state equal to the charge on the ion.
  • During displacement reactions, the oxidation states of the two metal species involved change:
    • Metal elements increase their oxidation state, as they lose electrons.
    • Metal ions decrease their oxidation state, as they gain electrons.
  • The sum of the oxidation states for the elements in a molecule is zero.
  • In most compounds:
    • Hydrogen has an oxidation state of one.
    • Oxygen has an oxidation state of negative two.
  • Oxidation states can be used to describe electron transfer in oxidation-reduction reactions:
    • Oxidation involves an increase in oxidation state.
    • Reduction involves a decrease in oxidation state.

Easychem - Oxidation state


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