Valency

In chemistry, valency is the power of an atom of an element to combine with other atoms measured by the number of electrons which an atom will give, take, or share to form a chemical compound. This is related to the number of spaces left in an atom's electron shells, which is why the only elements with valencies of zero are the noble gases.

See also: Chemical affinity, oxidation number

List of valencies for the first 103 elements in order of atomic number:

Atomic number		Name of element		Valency
1		Hydrogen		1
2		Helium		0
3		Lithium		1
4		Beryllium		2
5		Boron		3
6		Carbon		2, 4
7		Nitrogen		3, 5
8		Oxygen		2
9		Fluorine		1
10		Neon		0
11		Sodium		1
12		Magnesium		2
13		Aluminium		3
14		Silicon		4
15		Phosphorus		3, 5
16		Sulphur		2, 4, 6
17		Chlorine		1, 3, 5, 7
18		Argon		0
19		Potassium		1
20		Calcium		3, 5
21		Scandium		3
22		Titanium		3, 4
23		Vanadium		2, 3, 4, 5
24		Chromium		2, 3, 6
25		Manganese		2, 3, 4, 6, 7
26		Iron		2, 3
27		Cobalt		2, 3
28		Nickel		2, 3
29		Copper		1, 2
30		Zinc		2
31		Gallium		2, 3
32		Germanium		4
33		Arsenic		3, 5
34		Selenium		2, 4, 6
35		Bromine		1, 3, 5, 7
36		Krypton		0
37		Rubidium		1
38		Strontium		2
39		Yttrium		3
40		Zirconium		4
41		Niobium		3, 5
42		Molybdenum		2, 3, 4, 5, 6
43		Technetium		2, 3, 4, 6, 7
44		Ruthenium		3, 4, 6, 8
45		Rhodium		3, 4
46		Palladium		2, 4
47		Silver		1
48		Cadmium		2
49		Indium		1, 3
50		Tin		2, 4
51		Antimony		3, 5
52		Tellurium		2, 4, 6
53		Iodine		1, 3, 5, 7
54		Xenon		0
55		Caesium		1
56		Barium		2
57		Lanthanum		3
58		Cerium		3, 4
59		Praseodymium		3
60		Neodymium		3
61		Promethium		3
62		Samarium		2, 3
63		Europium		2, 3
64		Gadolinium		3
65		Terbium		3
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, 5
74		Tungsten		2, 4, 5, 6
75		Rhenium		1, 4, 7
76		Osmium		2, 3, 4, 6, 8
77		Iridium		3, 4
78		Platinum		2, 4
79		Gold		1, 3
80		Mercury		1, 2
81		Thallium		1, 3
82		Lead		2, 4
83		Bismuth		3, 5
84		Polonium		2, 3, 4
85		Astatine		1, 3, 5, 7
86		Radon		0
87		Francium		1
88		Radium		2
89		Actinium		3
90		Thorium		4
91		Protactinium		4, 5
92		Uranium		3, 4, 5, 6
93		Neptunium		2, 3, 4, 5, 6
94		Plutonium		2, 3, 4, 5, 6
95		Americium		2, 3, 4, 5, 6
96		Curium		2, 3, 4
97		Berkelium		2, 3, 4
98		Californium		2, 3, 4
99		Einsteinium		2, 3
100		Fermium		2, 3
101		Mendelevium		2, 3
102		Nobelium		2, 3
103		Lawrencium		3