the number of electrons an atom loses, gains, or shares when it forms chemical bonds
are a measure of the atoms combining capacity
can be determined by finding the number of electrons in outer energy level
if atom loses electrons (forms positive ions), oxidation number is positive
if atom gains electrons(forms negative ions), oxidation number is negative
can also be determined by knowing elements location on Periodic Table
Group
1
2
3-12
13
14
15
16
17
18
Oxidation Number
+1
+2
varies most have more than one
+3
+/-4
-3
-2
-1
0
transition elements can have more than one oxidation number (will be designated by the charge on ion or by a roman numeral following elements name, i.e., Iron III has oxidation number of +3
we can use oxidation numbers to predict the formula of a compound
the sum of the oxidation numbers in a compound must equal zero
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