Pure Appl. Chem., 73, 667-683 (2001) The standard values and/or errors for nitrogen, sulfur, chlorine, germanium, xenon, erbium and uranium have been revised. Elements 114, 116 and 118 have been added (but see note below). The most stable radionuclide for seaborgium, hassium, elements 110 and 112 have been revised.
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 Lett. 1999, 83, 1104] for elements 116 and 118 has been withdrawn [see Chem.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); Phys. Rev. Lett. in press]
Previous values may be consulted from the 1993 table, the 1995 table or 1997 table
The original paper should be consulted for details of the half life of the radioisotopes quoted below. In addition there are recommendations on the scales for quoting relative isotope-ratio data for stable hydrogen, lithium, carbon, oxygen and sulfur. 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 | 65.39(2) | 7 |
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 | 83.80(1) | 1, 3, 7 |
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(1) | 1, 7 |
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 | 162.50(3) | 1, 7 |
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 | Uun | Ununnilium | [281] | 5, 6 |
111 | Uuu | Unununium | [272] | 5, 6 |
112 | Uub | Ununbium | [285] | 5, 6 |
114 | Uuq | Ununquadium | [289] | 5, 6 |
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 |
105 | Db | Dubnium | [262] | 5, 6 |
66 | Dy | Dysprosium | 162.50(3) | 1, 7 |
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 | 83.80(1) | 1, 3, 7 |
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(1) | 1, 7 |
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) | |
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 | |
110 | Uun | Ununnilium | [281] | 5, 6 |
118 | Uuo | Ununoctium | see Note above | |
114 | Uuq | Ununquadium | [289] | 5, 6 |
111 | Uuu | Unununium | [272] | 5, 6 |
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 | 65.39(2) | 7 |
40 | Zr | Zirconium | 91.224(2) | 1 |