Sun December 04, 2011 By:

what is oxidation state?

Expert Reply
Sun December 04, 2011

The oxidation state is an indication of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. 

The guidelines for assigning oxidation states (numbers) are given below:

  1. The oxidation state of any element such as Fe, H2, O2, P4, S8 is zero (0).
  2. The oxidation state of oxygen in its compounds is -2, except for peroxides like H2O2, and Na2O2, in which the oxidation state for O is -1.
  3. The oxidation state of hydrogen is +1 in its compounds, except for metal hydrides, such as NaH, LiH, etc., in which the oxidation state for H is -1.
  4. The oxidation states of other elements are then assigned to make the algebraic sum of the oxidation states equal to the net charge on the molecule or ion.
  5. The following elements usually have the same oxidation states in their compounds:
  • +1 for alkali metals - Li, Na, K, Rb, Cs;
  • +2 for alkaline earth metals - Be, Mg, Ca, Sr, Ba;
  • -1 for halogens except when they form compounds with oxygen or one another;


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