Problem: What is the oxidation state of an individual phosphorus atom in PO33 − ?Oxidation states are important for keeping track of electrons in oxidation-reduction reactions. Here are some general rules to remember:Atoms of a free element have an oxidation number of 0.Monoatomic ions have an oxidation state equal to their chargePolyatomic ions and neutral molecules have a charge equal to the charge on the species.Metals in compounds have positive oxidation states. Group 1A and 2A metals have oxidations states of +1 and +2 respectively.Nonmetals in compounds have oxidation states with the priority listed:Fluorine oxidation state of − 1Hydrogen oxidation state of +1Oxygen oxidation state of − 2Group 7A nonmetals oxidation state of − 1Group 6A nonmetals oxidation state of − 2Group 5A nonmetals oxidation state of − 3Elements not covered: the sum of the charges of all elements must equal the charge on the species. Thus, follow the rules in the fourth and fifth bullet points first, and deduce the oxidation state once all others have been assigned.IonsIn an ion, the sum of the oxidation states is equal to the overall ionic charge. Note that the sign of the oxidation states and the number of atoms associated with each oxidation state must beconsidered. In OH − , for example, the oxygen atom has an oxidation state of − 2 and the hydrogen atom has an oxidation state of +1, for a total of ( − 2) + ( + 1) = − 1.

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What is the oxidation state of an individual phosphorus atom in PO33 − ?

Oxidation states are important for keeping track of electrons in oxidation-reduction reactions. Here are some general rules to remember:

  • Atoms of a free element have an oxidation number of 0.
  • Monoatomic ions have an oxidation state equal to their charge
  • Polyatomic ions and neutral molecules have a charge equal to the charge on the species.
  • Metals in compounds have positive oxidation states. Group 1A and 2A metals have oxidations states of +1 and +2 respectively.
  • Nonmetals in compounds have oxidation states with the priority listed:
  • Fluorine oxidation state of − 1
  • Hydrogen oxidation state of +1
  • Oxygen oxidation state of − 2
  • Group 7A nonmetals oxidation state of − 1
  • Group 6A nonmetals oxidation state of − 2
  • Group 5A nonmetals oxidation state of − 3

Elements not covered: the sum of the charges of all elements must equal the charge on the species. Thus, follow the rules in the fourth and fifth bullet points first, and deduce the oxidation state once all others have been assigned.

Ions

In an ion, the sum of the oxidation states is equal to the overall ionic charge. Note that the sign of the oxidation states and the number of atoms associated with each oxidation state must be
considered. In OH − , for example, the oxygen atom has an oxidation state of − 2 and the hydrogen atom has an oxidation state of +1, for a total of ( − 2) + ( + 1) = − 1.

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