Oxidation Number Rules Flashcards
1
Q
Free (uncombined) elements
A
Free (uncombined) elements have an oxidation number of zero
This includes polyatomic elements
2
Q
Monatomic ions
A
Monatomic ions:
Oxidation number = charge of ion
3
Q
Oxygen
A
Oxygen:
Usually -2
Exceptions:
Hydrogen peroxide: H2O2 (-1)
Peroxide ion: O22- (-1)
4
Q
Hydrogen
A
Hydrogen:
Oxidation = +1
Except when bound to metals in binary compounds (-1)
5
Q
Group 1A
A
Group 1A:
+1
6
Q
Group 2A
A
Group 2A:
+2
7
Q
Al (Group 3A)
A
Al (Group 3A):
+3
8
Q
F (Group 7A)
A
F (Group 7A):
-1
9
Q
Molecular formula or formula unit
A
Molecular formula or formula unit:
Oxidation number sum must equal zero
10
Q
Polyatomic ions
A
Polyatomic ions:
Sum of oxidation numbers must = ion charge
11
Q
Oxidation numbers
A
Can be integers or fractions
E.g. one O in O2- = -1/2
