What Is Valence or Valency?

The terms have two related meanings in chemistry

Valence
Valence is a measure of how readily an atom or radical forms a bond. Jason Reed / Getty Images

The words valence and valency have two related meanings in chemistry.

Valence describes how easily an atom or radical can combine with other chemical species. This is determined based on the number of electrons that would be added, lost, or shared if it reacts with other atoms.

Valence is denoted using a positive or negative integer used to represent this binding capacity. For example, common valences of copper are 1 and 2.

Table of Element Valences

Number Element Valence
1Hydrogen(-1), +1
2Helium0
3Lithium+1
4Beryllium+2
5Boron-3, +3
6Carbon(+2), +4
7Nitrogen-3, -2, -1, (+1), +2, +3, +4, +5
8Oxygen-2
9Fluorine-1, (+1)
10Neon0
11Sodium+1
12Magnesium+2
13Aluminum+3
14Silicon-4, (+2), +4
15Phosphorus-3, +1, +3, +5
16Sulfur-2, +2, +4, +6
17Chlorine-1, +1, (+2), +3, (+4), +5, +7
18Argon0
19Potassium+1
20Calcium+2
21Scandium+3
22Titanium+2, +3, +4
23Vanadium+2, +3, +4, +5
24Chromium+2, +3, +6
25Manganese+2, (+3), +4, (+6), +7
26Iron+2, +3, (+4), (+6)
27Cobalt+2, +3, (+4)
28Nickel(+1), +2, (+3), (+4)
29Copper+1, +2, (+3)
30Zinc+2
31Gallium(+2). +3
32Germanium-4, +2, +4
33Arsenic-3, (+2), +3, +5
34Selenium-2, (+2), +4, +6
35Bromine-1, +1, (+3), (+4), +5
36Krypton0
37Rubidium+1
38Strontium+2
39Yttrium+3
40Zirconium(+2), (+3), +4
41Niobium(+2), +3, (+4), +5
42Molybdenum(+2), +3, (+4), (+5), +6
43Technetium+6
44Ruthenium(+2), +3, +4, (+6), (+7), +8
45Rhodium(+2), (+3), +4, (+6)
46Palladium+2, +4, (+6)
47Silver+1, (+2), (+3)
48Cadmium(+1), +2
49Indium(+1), (+2), +3
50Tin+2, +4
51Antimony-3, +3, (+4), +5
52Tellurium-2, (+2), +4, +6
53Iodine-1, +1, (+3), (+4), +5, +7
54Xenon0
55Cesium+1
56Barium+2
57Lanthanum+3
58Cerium+3, +4
59Praseodymium+3
60Neodymium+3, +4
61Promethium+3
62Samarium(+2), +3
63Europium(+2), +3
64Gadolinium+3
65Terbium+3, +4
66Dysprosium+3
67Holmium+3
68Erbium+3
69Thulium(+2), +3
70Ytterbium(+2), +3
71Lutetium+3
72Hafnium+4
73Tantalum(+3), (+4), +5
74Tungsten(+2), (+3), (+4), (+5), +6
75Rhenium(-1), (+1), +2, (+3), +4, (+5), +6, +7
76Osmium(+2), +3, +4, +6, +8
77Iridium(+1), (+2), +3, +4, +6
78Platinum(+1), +2, (+3), +4, +6
79Gold+1, (+2), +3
80Mercury+1, +2
81Thallium+1, (+2), +3
82Lead+2, +4
83Bismuth(-3), (+2), +3, (+4), (+5)
84Polonium(-2), +2, +4, (+6)
85Astatine?
86Radon0
87Francium?
88Radium+2
89Actinium+3
90Thorium+4
91Protactinium+5
92Uranium(+2), +3, +4, (+5), +6