Values from the 2001 table Pure Appl. Chem., 75, 1107-1122 (2003). A PDF of the printed version is available. The values of zinc, krypton, molybdenum and dysprosium have been modified. The approved name for element 110 is included, see Pure Appl. Chem., 75, 1613-1615 (2003). The approved name for element 111 is also included, see Pure Appl. Chem., 76, 2101-2103 (2004).
World Wide Web version of atomic weight data prepared by G. P. Moss, originally from a file provided by D. R. Lide.
Note The claim [Phys. Rev. Lett. 1999, 83, 1104] for elements 116 and 118 has been withdrawn [see Chem. Eng. News 2001, 79, 10 (6 August 2001); 2002, 80, 12 (22 July 2002);Phys. Rev. Lett. 2002, 89, 039901]
Previous values may be consulted from the 1993 table, the 1995 table, the 1997 table or the 1999 table.
The original paper should be consulted for details of the half life of the radioisotopes quoted below. Also there is a report on the different isotopic compositions of some non-terrestrial materials.
A number in parentheses indicates the uncertainty in the last digit of the atomic weight.
See also a copy of the periodic table with atomic weights to five significant figures.
See also below the list in Name order.
At No | Symbol | Name | Atomic Wt | Notes |
1 | H | Hydrogen | 1.00794(7) | 1, 2, 3 |
2 | He | Helium | 4.002602(2) | 1, 2 |
3 | Li | Lithium | [6.941(2)] | 1, 2, 3, 4 |
4 | Be | Beryllium | 9.012182(3) | |
5 | B | Boron | 10.811(7) | 1, 2, 3 |
6 | C | Carbon | 12.0107(8) | 1, 2 |
7 | N | Nitrogen | 14.0067(2) | 1, 2 |
8 | O | Oxygen | 15.9994(3) | 1, 2 |
9 | F | Fluorine | 18.9984032(5) | |
10 | Ne | Neon | 20.1797(6) | 1, 3 |
11 | Na | Sodium | 22.989770(2) | |
12 | Mg | Magnesium | 24.3050(6) | |
13 | Al | Aluminium | 26.981538(2) | |
14 | Si | Silicon | 28.0855(3) | 2 |
15 | P | Phosphorus | 30.973761(2) | |
16 | S | Sulfur | 32.065(5) | 1, 2 |
17 | Cl | Chlorine | 35.453(2) | 3 |
18 | Ar | Argon | 39.948(1) | 1, 2 |
19 | K | Potassium | 39.0983(1) | 1 |
20 | Ca | Calcium | 40.078(4) | 1 |
21 | Sc | Scandium | 44.955910(8) | |
22 | Ti | Titanium | 47.867(1) | |
23 | V | Vanadium | 50.9415(1) | |
24 | Cr | Chromium | 51.9961(6) | |
25 | Mn | Manganese | 54.938049(9) | |
26 | Fe | Iron | 55.845(2) | |
27 | Co | Cobalt | 58.933200(9) | |
28 | Ni | Nickel | 58.6934(2) | |
29 | Cu | Copper | 63.546(3) | 2 |
30 | Zn | Zinc | 65.409(4) | |
31 | Ga | Gallium | 69.723(1) | |
32 | Ge | Germanium | 72.64(1) | |
33 | As | Arsenic | 74.92160(2) | |
34 | Se | Selenium | 78.96(3) | |
35 | Br | Bromine | 79.904(1) | |
36 | Kr | Krypton | 83.798(2) | 1, 3 |
37 | Rb | Rubidium | 85.4678(3) | 1 |
38 | Sr | Strontium | 87.62(1) | 1, 2 |
39 | Y | Yttrium | 88.90585(2) | |
40 | Zr | Zirconium | 91.224(2) | 1 |
41 | Nb | Niobium | 92.90638(2) | |
42 | Mo | Molybdenum | 95.94(2) | 1 |
43 | Tc | Technetium | [98] | 5 |
44 | Ru | Ruthenium | 101.07(2) | 1 |
45 | Rh | Rhodium | 102.90550(2) | |
46 | Pd | Palladium | 106.42(1) | 1 |
47 | Ag | Silver | 107.8682(2) | 1 |
48 | Cd | Cadmium | 112.411(8) | 1 |
49 | In | Indium | 114.818(3) | |
50 | Sn | Tin | 118.710(7) | 1 |
51 | Sb | Antimony | 121.760(1) | 1 |
52 | Te | Tellurium | 127.60(3) | 1 |
53 | I | Iodine | 126.90447(3) | |
54 | Xe | Xenon | 131.293(6) | 1, 3 |
55 | Cs | Caesium | 132.90545(2) | |
56 | Ba | Barium | 137.327(7) | |
57 | La | Lanthanum | 138.9055(2) | 1 |
58 | Ce | Cerium | 140.116(1) | 1 |
59 | Pr | Praseodymium | 140.90765(2) | |
60 | Nd | Neodymium | 144.24(3) | 1 |
61 | Pm | Promethium | [145] | 5 |
62 | Sm | Samarium | 150.36(3) | 1 |
63 | Eu | Europium | 151.964(1) | 1 |
64 | Gd | Gadolinium | 157.25(3) | 1 |
65 | Tb | Terbium | 158.92534(2) | |
66 | Dy | Dysprosium | 162.500(1) | 1 |
67 | Ho | Holmium | 164.93032(2) | |
68 | Er | Erbium | 167.259(3) | 1 |
69 | Tm | Thulium | 168.93421(2) | |
70 | Yb | Ytterbium | 173.04(3) | 1 |
71 | Lu | Lutetium | 174.967(1) | 1 |
72 | Hf | Hafnium | 178.49(2) | |
73 | Ta | Tantalum | 180.9479(1) | |
74 | W | Tungsten | 183.84(1) | |
75 | Re | Rhenium | 186.207(1) | |
76 | Os | Osmium | 190.23(3) | 1 |
77 | Ir | Iridium | 192.217(3) | |
78 | Pt | Platinum | 195.078(2) | |
79 | Au | Gold | 196.96655(2) | |
80 | Hg | Mercury | 200.59(2) | |
81 | Tl | Thallium | 204.3833(2) | |
82 | Pb | Lead | 207.2(1) | 1, 2 |
83 | Bi | Bismuth | 208.98038(2) | |
84 | Po | Polonium | [209] | 5 |
85 | At | Astatine | [210] | 5 |
86 | Rn | Radon | [222] | 5 |
87 | Fr | Francium | [223] | 5 |
88 | Ra | Radium | [226] | 5 |
89 | Ac | Actinium | [227] | 5 |
90 | Th | Thorium | 232.0381(1) | 1, 5 |
91 | Pa | Protactinium | 231.03588(2) | 5 |
92 | U | Uranium | 238.02891(3) | 1, 3, 5 |
93 | Np | Neptunium | [237] | 5 |
94 | Pu | Plutonium | [244] | 5 |
95 | Am | Americium | [243] | 5 |
96 | Cm | Curium | [247] | 5 |
97 | Bk | Berkelium | [247] | 5 |
98 | Cf | Californium | [251] | 5 |
99 | Es | Einsteinium | [252] | 5 |
100 | Fm | Fermium | [257] | 5 |
101 | Md | Mendelevium | [258] | 5 |
102 | No | Nobelium | [259] | 5 |
103 | Lr | Lawrencium | [262] | 5 |
104 | Rf | Rutherfordium | [261] | 5, 6 |
105 | Db | Dubnium | [262] | 5, 6 |
106 | Sg | Seaborgium | [266] | 5, 6 |
107 | Bh | Bohrium | [264] | 5, 6 |
108 | Hs | Hassium | [277] | 5, 6 |
109 | Mt | Meitnerium | [268] | 5, 6 |
110 | Ds | Darmstadtium | [281] | 5, 6 |
111 | Rg | Roentgenium | [272] | 5, 6 |
112 | Uub | Ununbium | [285] | 5, 6 |
113 | Uut | Ununtrium | [284] | 5, 7 |
114 | Uuq | Ununquadium | [289] | 5, 6 |
115 | Uup | Ununpentium | [288] | 5, 7 |
116 | Uuh | Ununhexium | see Note above | |
118 | Uuo | Ununoctium | see Note above |
At No | Symbol | Name | Atomic Wt | Notes |
89 | Ac | Actinium | [227] | 5 |
13 | Al | Aluminium | 26.981538(2) | |
95 | Am | Americium | [243] | 5 |
51 | Sb | Antimony | 121.760(1) | 1 |
18 | Ar | Argon | 39.948(1) | 1, 2 |
33 | As | Arsenic | 74.92160(2) | |
85 | At | Astatine | [210] | 5 |
56 | Ba | Barium | 137.327(7) | |
97 | Bk | Berkelium | [247] | 5 |
4 | Be | Beryllium | 9.012182(3) | |
83 | Bi | Bismuth | 208.98038(2) | |
107 | Bh | Bohrium | [264] | 5, 6 |
5 | B | Boron | 10.811(7) | 1, 2, 3 |
35 | Br | Bromine | 79.904(1) | |
48 | Cd | Cadmium | 112.411(8) | 1 |
55 | Cs | Caesium | 132.90545(2) | |
20 | Ca | Calcium | 40.078(4) | 1 |
98 | Cf | Californium | [251] | 5 |
6 | C | Carbon | 12.0107(8) | 1, 2 |
58 | Ce | Cerium | 140.116(1) | 1 |
17 | Cl | Chlorine | 35.453(2) | 3 |
24 | Cr | Chromium | 51.9961(6) | |
27 | Co | Cobalt | 58.933200(9) | |
29 | Cu | Copper | 63.546(3) | 2 |
96 | Cm | Curium | [247] | 5 |
110 | Ds | Darmstadtium | [281] | 5, 6 |
105 | Db | Dubnium | [262] | 5, 6 |
66 | Dy | Dysprosium | 162.500(1) | 1 |
99 | Es | Einsteinium | [252] | 5 |
68 | Er | Erbium | 167.259(3) | 1 |
63 | Eu | Europium | 151.964(1) | 1 |
100 | Fm | Fermium | [257] | 5 |
9 | F | Fluorine | 18.9984032(5) | |
87 | Fr | Francium | [223] | 5 |
64 | Gd | Gadolinium | 157.25(3) | 1 |
31 | Ga | Gallium | 69.723(1) | |
32 | Ge | Germanium | 72.64(1) | |
79 | Au | Gold | 196.96655(2) | |
72 | Hf | Hafnium | 178.49(2) | |
108 | Hs | Hassium | [277] | 5, 6 |
2 | He | Helium | 4.002602(2) | 1, 2 |
67 | Ho | Holmium | 164.93032(2) | |
1 | H | Hydrogen | 1.00794(7) | 1, 2, 3 |
49 | In | Indium | 114.818(3) | |
53 | I | Iodine | 126.90447(3) | |
77 | Ir | Iridium | 192.217(3) | |
26 | Fe | Iron | 55.845(2) | |
36 | Kr | Krypton | 83.798(2) | 1, 3 |
57 | La | Lanthanum | 138.9055(2) | 1 |
103 | Lr | Lawrencium | [262] | 5 |
82 | Pb | Lead | 207.2(1) | 1, 2 |
3 | Li | Lithium | [6.941(2)] | 1, 2, 3, 4 |
71 | Lu | Lutetium | 174.967(1) | 1 |
12 | Mg | Magnesium | 24.3050(6) | |
25 | Mn | Manganese | 54.938049(9) | |
109 | Mt | Meitnerium | [268] | 5, 6 |
101 | Md | Mendelevium | [258] | 5 |
80 | Hg | Mercury | 200.59(2) | |
42 | Mo | Molybdenum | 95.94(2) | 1 |
60 | Nd | Neodymium | 144.24(3) | 1 |
10 | Ne | Neon | 20.1797(6) | 1, 3 |
93 | Np | Neptunium | [237] | 5 |
28 | Ni | Nickel | 58.6934(2) | |
41 | Nb | Niobium | 92.90638(2) | |
7 | N | Nitrogen | 14.0067(2) | 1, 2 |
102 | No | Nobelium | [259] | 5 |
76 | Os | Osmium | 190.23(3) | 1 |
8 | O | Oxygen | 15.9994(3) | 1, 2 |
46 | Pd | Palladium | 106.42(1) | 1 |
15 | P | Phosphorus | 30.973761(2) | |
78 | Pt | Platinum | 195.078(2) | |
94 | Pu | Plutonium | [244] | 5 |
84 | Po | Polonium | [209] | 5 |
19 | K | Potassium | 39.0983(1) | 1 |
59 | Pr | Praseodymium | 140.90765(2) | |
61 | Pm | Promethium | [145] | 5 |
91 | Pa | Protactinium | 231.03588(2) | 5 |
88 | Ra | Radium | [226] | 5 |
86 | Rn | Radon | [222] | 5 |
75 | Re | Rhenium | 186.207(1) | |
45 | Rh | Rhodium | 102.90550(2) | |
111 | Rg | Roentgenium | [272] | 5, 6 |
37 | Rb | Rubidium | 85.4678(3) | 1 |
44 | Ru | Ruthenium | 101.07(2) | 1 |
104 | Rf | Rutherfordium | [261] | 5, 6 |
62 | Sm | Samarium | 150.36(3) | 1 |
21 | Sc | Scandium | 44.955910(8) | |
106 | Sg | Seaborgium | [266] | 5, 6 |
34 | Se | Selenium | 78.96(3) | |
14 | Si | Silicon | 28.0855(3) | 2 |
47 | Ag | Silver | 107.8682(2) | 1 |
11 | Na | Sodium | 22.989770(2) | |
38 | Sr | Strontium | 87.62(1) | 1, 2 |
16 | S | Sulfur | 32.065(5) | 1, 2 |
73 | Ta | Tantalum | 180.9479(1) | |
43 | Tc | Technetium | [98] | 5 |
52 | Te | Tellurium | 127.60(3) | 1 |
65 | Tb | Terbium | 158.92534(2) | |
81 | Tl | Thallium | 204.3833(2) | |
90 | Th | Thorium | 232.0381(1) | 1, 5 |
69 | Tm | Thulium | 168.93421(2) | |
50 | Sn | Tin | 118.710(7) | 1 |
22 | Ti | Titanium | 47.867(1) | |
74 | W | Tungsten | 183.84(1) | |
112 | Uub | Ununbium | [285] | 5, 6 |
116 | Uuh | Ununhexium | see Note above | |
118 | Uuo | Ununoctium | see Note above | |
115 | Uup | Ununpentium | [288] | 5, 7 |
114 | Uuq | Ununquadium | [289] | 5, 6 |
113 | Uut | Ununtrium | [284] | 5, 7 |
92 | U | Uranium | 238.02891(3) | 1, 3, 5 |
23 | V | Vanadium | 50.9415(1) | |
54 | Xe | Xenon | 131.293(6) | 1, 3 |
70 | Yb | Ytterbium | 173.04(3) | 1 |
39 | Y | Yttrium | 88.90585(2) | |
30 | Zn | Zinc | 65.409(4) | |
40 | Zr | Zirconium | 91.224(2) | 1 |