Calculating the Oxidaiton Number

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Rules for calculating the Oxidation number:
  1.  Free elements( Single atoms) like C, Fe, Zn, H, He, Li etc. have oxidaition number equal to 0.
  2. In Homonuclear species like H2, Cl2, Br2, O2 etc. each atom of that molecule have oxidation number 0.
  3. The sum of oxidation number of elements in a compound is zero. For example : ForCaCO3Oxidation number of Ca + Oxidation number of C + 3 × Oxidation number of O = 0
  4. The sum of oxidation number for radicals( Charge carrying species) is equal to their charge. For example:SO4- -Oxidation number of S + 4 × Oxidation number of O = -2NH4+Oxidation number of N  + 4 × Oxidation number of H = +1
  5. The oxidation number of metals is generally positive. For example: Na = +1, K = +1, Mg = +2 etc.
  6. The oxidation number of hydrogen atom is generally +1 but -1 in case of metal hydrides.
  7. The oxidation number of Oxygen atom is generally -2 but in case of super oxides is -(1/2) and in case of peroxides is -1.
  8. The oxidation number of Cl, Br, I, F is -1 generally. Fluorine has oxidation number -1 always but Cl, Br and I may have different oxidation number when combined with oxygen.

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