Oxidation Numbers

Front

What is an oxidation number?

Back

The oxidation number is a value that represents the total number of electrons that an atom either gains or loses in a chemical reaction, indicating its degree of oxidation or reduction.

Front

What is the oxidation number of hydrogen (H) in most compounds?

Back

+1, except when bonded to metals in binary compounds where it is -1.

Front

What is the oxidation number of oxygen (O) in most compounds?

Back

-2, except in peroxides where it is -1 and in OF2 where it is +2.

Front

What is the oxidation number of alkali metals (Group 1) in compounds?

Back

+1.

Front

What is the oxidation number of alkaline earth metals (Group 2) in compounds?

Back

+2.

Front

What is the oxidation number of halogens (Group 17) in compounds?

Back

-1, unless they are bonded to a more electronegative element.

Front

How do you determine the oxidation number of an element in a compound?

Back

By using the known oxidation states of other elements in the compound and ensuring the sum of oxidation numbers equals the overall charge of the compound.

Front

What is the oxidation number of sulfur (S) in sulfate (SO4^2-)?

Back

+6.

Front

What is the oxidation number of phosphorus (P) in phosphate (PO4^3-)?

Back

+5.

Front

What is the oxidation number of iron (Fe) in iron(II) oxide (FeO)?

Back

+2.