Things to Memorize Section 4.4
Oxidation Numbers
1. For an atom in its elemental form, the oxidation number is ALWAYS zero
2. For any monatomic ion, the oxidation number equals the charge
3. Nonmetals usually have negative oxidation numbers although they can sometimes be positive
a. Oxygen usually has an oxidation number of -2 except for when it is in the peroxide ion where each oxygen atom has an oxidation number of -1
b. Hydrogen usually has an oxidation number of +1 when bonded to nonmentals and -1 when bonded to metals
c. Fluorine is -1 in ALL compounds.
d. Other halogens have an oxidation number of -1 in MOST binary compounds. However, when combined with oxygen they have positive oxidation states.
4. The sum of the oxidation numbers of all atoms in a neutral compound is zero. The sum of the oxidation numbers in a polyatomic ion are equal to the charge of the ion.
