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
By
Anne Marie Helmenstine, Ph.D.
Anne Marie Helmenstine, Ph.D.
Chemistry Expert
  • Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
  • B.A., Physics and Mathematics, Hastings College
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
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Updated on September 30, 2018

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

Valence is a measure of outer shell electrons.
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Valence Definition in Chemistry
By Anne Marie Helmenstine, Ph.D.

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
1 Hydrogen (-1), +1
2 Helium 0
3 Lithium +1
4 Beryllium +2
5 Boron -3, +3
6 Carbon (+2), +4
7 Nitrogen -3, -2, -1, (+1), +2, +3, +4, +5
8 Oxygen -2
9 Fluorine -1, (+1)
10 Neon 0
11 Sodium +1
12 Magnesium +2
13 Aluminum +3
14 Silicon -4, (+2), +4
15 Phosphorus -3, +1, +3, +5
16 Sulfur -2, +2, +4, +6
17 Chlorine -1, +1, (+2), +3, (+4), +5, +7
18 Argon 0
19 Potassium +1
20 Calcium +2
21 Scandium +3
22 Titanium +2, +3, +4
23 Vanadium +2, +3, +4, +5
24 Chromium +2, +3, +6
25 Manganese +2, (+3), +4, (+6), +7
26 Iron +2, +3, (+4), (+6)
27 Cobalt +2, +3, (+4)
28 Nickel (+1), +2, (+3), (+4)
29 Copper +1, +2, (+3)
30 Zinc +2
31 Gallium (+2). +3
32 Germanium -4, +2, +4
33 Arsenic -3, (+2), +3, +5
34 Selenium -2, (+2), +4, +6
35 Bromine -1, +1, (+3), (+4), +5
36 Krypton 0
37 Rubidium +1
38 Strontium +2
39 Yttrium +3
40 Zirconium (+2), (+3), +4
41 Niobium (+2), +3, (+4), +5
42 Molybdenum (+2), +3, (+4), (+5), +6
43 Technetium +6
44 Ruthenium (+2), +3, +4, (+6), (+7), +8
45 Rhodium (+2), (+3), +4, (+6)
46 Palladium +2, +4, (+6)
47 Silver +1, (+2), (+3)
48 Cadmium (+1), +2
49 Indium (+1), (+2), +3
50 Tin +2, +4
51 Antimony -3, +3, (+4), +5
52 Tellurium -2, (+2), +4, +6
53 Iodine -1, +1, (+3), (+4), +5, +7
54 Xenon 0
55 Cesium +1
56 Barium +2
57 Lanthanum +3
58 Cerium +3, +4
59 Praseodymium +3
60 Neodymium +3, +4
61 Promethium +3
62 Samarium (+2), +3
63 Europium (+2), +3
64 Gadolinium +3
65 Terbium +3, +4
66 Dysprosium +3
67 Holmium +3
68 Erbium +3
69 Thulium (+2), +3
70 Ytterbium (+2), +3
71 Lutetium +3
72 Hafnium +4
73 Tantalum (+3), (+4), +5
74 Tungsten (+2), (+3), (+4), (+5), +6
75 Rhenium (-1), (+1), +2, (+3), +4, (+5), +6, +7
76 Osmium (+2), +3, +4, +6, +8
77 Iridium (+1), (+2), +3, +4, +6
78 Platinum (+1), +2, (+3), +4, +6
79 Gold +1, (+2), +3
80 Mercury +1, +2
81 Thallium +1, (+2), +3
82 Lead +2, +4
83 Bismuth (-3), (+2), +3, (+4), (+5)
84 Polonium (-2), +2, +4, (+6)
85 Astatine ?
86 Radon 0
87 Francium ?
88 Radium +2
89 Actinium +3
90 Thorium +4
91 Protactinium +5
92 Uranium (+2), +3, +4, (+5), +6
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Helmenstine, Anne Marie, Ph.D. "What Is Valence or Valency?" ThoughtCo, Aug. 27, 2020, thoughtco.com/what-is-valence-or-valency-606459. Helmenstine, Anne Marie, Ph.D. (2020, August 27). What Is Valence or Valency? Retrieved from https://www.thoughtco.com/what-is-valence-or-valency-606459 Helmenstine, Anne Marie, Ph.D. "What Is Valence or Valency?" ThoughtCo. https://www.thoughtco.com/what-is-valence-or-valency-606459 (accessed April 27, 2024).