Current Table of Standard Atomic Weights Abridged to Five Significant Figures
Atomic Weights of the Elements 1993, Pure Appl. Chem. 66, 2423-2444 (1994).
[full text - pdf 1200 KB] {TSAW 1993.pdf}
Table of Standard Atomic Weights Abridged to Five Significant Figures
Atomic weights, scaled to the relative atomic mass, Ar(12C) = 12, are here quoted to five significant figures unless the dependable accuracy is more limited by either the combined uncertainties of the best published atomic weight determinations, or by the variability of isotopic composition in normal terrestrial occurrences (the latter applies to elements annotated r). The last significant figure of each tabulated value is considered reliable to ±1 except when a larger single digit uncertainty is inserted in parentheses following the atomic weight. Neither the highest nor the lowest actual atomic weight of any normal sample is thought likely to differ from the tabulated value by more than the assigned uncertainty. However, the tabulated values do not apply either to samples of highly exceptional isotopic composition arising from most unusual geological occurrences (for elements annotated g) or to those whose isotopic composition has been artificially altered. Such might even be found in commerce without disclosure of that modification (for elements annotated m). Elements annotated by an asterisk (*) have no stable isotope and are generally represented in this Table by just one of the element's commonly known radioisotopes, with a corresponding relative atomic mass in the atomic weight column. However, three such elements (Th, Pa, and U) do have a characteristic terrestrial isotopic composition, and for these an atomic weight is tabulated. For more detailed information users should refer to the full IUPAC Table of Standard Atomic Weights.
Alphabetical Order in English |
Name |
Symbol |
Number |
Atomic Weight |
Footnotes |
Actinium* |
227Ac |
89 |
227.03 |
|
Aluminium (Aluminum) |
Al |
13 |
26.982 |
|
Americium* |
241Am |
95 |
241.06 |
|
Antimony (Stibium) |
Sb |
51 |
121.76 |
g |
Argon |
Ar |
18 |
39.948 |
g r |
Arsenic |
As |
33 |
74.922 |
|
Astatine* |
210At |
85 |
209.99 |
|
Barium |
Ba |
56 |
137.33 |
|
Berkelium* |
249Bk |
97 |
249.08 |
|
Beryllium |
Be |
4 |
9.0122 |
|
Bismuth |
Bi |
83 |
208.98 |
|
Boron |
B |
5 |
10.811(5) |
g m r |
Bromine |
Br |
35 |
79.904 |
|
Cadmium |
Cd |
48 |
112.41 |
|
Caesium (Cesium) |
Cs |
55 |
132.91 |
|
Calcium |
Ca |
20 |
40.078(4) |
g |
Californium* |
252Cf |
98 |
252.08 |
|
Carbon |
C |
6 |
12.011 |
g r |
Cerium |
Ce |
58 |
140.12 |
g |
Chlorine |
Cl |
17 |
35.453 |
m |
Chromium |
Cr |
24 |
51.996 |
|
Cobalt |
Co |
27 |
58.933 |
|
Copper (Cuprum) |
Cu |
29 |
63.546(3) |
r |
Curium* |
244Cm |
96 |
244.06 |
|
Dysprosium |
Dy |
66 |
162.50(3) |
g |
Einsteinium* |
252Es |
99 |
252.08 |
|
Erbium |
Er |
68 |
167.26(3) |
g |
Europium |
Eu |
63 |
151.96 |
g |
Fermium* |
257Fm |
100 |
257.10 |
|
Fluorine |
F |
9 |
18.998 |
|
Francium* |
223Fr |
87 |
223.02 |
|
Gadolinium |
Gd |
64 |
157.25(3) |
g |
Gallium |
Ga |
31 |
69.723 |
|
Germanium |
Ge |
32 |
72.61(2) |
|
Gold (Aurum) |
Au |
79 |
196.97 |
|
Hafnium |
Hf |
72 |
178.49(2) |
|
Helium |
He |
2 |
4.0026 |
|
Holmium |
Ho |
67 |
164.93 |
|
Hydrogen |
H |
1 |
1.007 9 |
g m |
Indium |
In |
49 |
114.82 |
|
Iodine |
I |
53 |
126.90 |
|
Iridium |
Ir |
77 |
192.22 |
|
Iron (Ferrum) |
Fe |
26 |
55.845(2) |
|
Krypton |
Kr |
36 |
83.80 |
g m |
Lanthanum |
La |
57 |
138.91 |
|
Lawrencium* |
262Lr |
103 |
262.11 |
|
Lead (Plumbum) |
Pb |
82 |
207.2 |
g r |
Lithium |
Li |
3 |
[6.941(2)]† |
g m r |
Lutetium |
Lu |
71 |
174.97 |
g |
Magnesium |
Mg |
12 |
24.305 |
|
Manganese |
Mn |
25 |
54.938 |
|
Mendelevium* |
258Md |
101 |
258.10 |
|
Mercury (Hydrargyrum) |
Hg |
80 |
200.59(2) |
|
Molybdenum |
Mo |
42 |
95.94 |
g |
Neodymium |
Nd |
60 |
144.24(3) |
g |
Neon |
Ne |
10 |
20.180 |
m |
Neptunium* |
237Np |
93 |
237.05 |
|
Nickel |
Ni |
28 |
58.693 |
|
Niobium |
Nb |
41 |
92.906 |
|
Nitrogen |
N |
7 |
14.007 |
|
Nobelium* |
259No |
102 |
259.10 |
|
Osmium |
Os |
76 |
190.23(3) |
g |
Oxygen |
O |
8 |
15.999 |
|
Palladium |
Pd |
46 |
106.42 |
g |
Phosphorus |
P |
15 |
30.974 |
|
Platinum |
Pt |
78 |
195.08(3) |
|
Plutonium* |
239Pu |
94 |
239.05 |
|
Polonium* |
210Po |
84 |
209.98 |
|
Potassium (Kalium) |
K |
19 |
39.098 |
g |
Praseodymium |
Pr |
59 |
140.91 |
|
Promethium* |
147Pm |
61 |
146.92 |
|
Protactinium* |
Pa |
91 |
231.04 |
|
Radium* |
226Ra |
88 |
226.03 |
|
Radon* |
222Rn |
86 |
222.02 |
|
Rhenium |
Re |
75 |
186.21 |
|
Rhodium |
Rh |
45 |
102.91 |
|
Rubidium |
Rb |
37 |
85.468 |
|
Ruthenium |
Ru |
44 |
101.07(2) |
g |
Samarium |
Sm |
62 |
150.36(3) |
g |
Scandium |
Sc |
21 |
44.956 |
|
Selenium |
Se |
34 |
78.96(3) |
|
Silicon |
Si |
14 |
28.086 |
|
Silver (Argentum) |
Ag |
47 |
107.87 |
|
Sodium (Natrium) |
Na |
11 |
22.990 |
|
Strontium |
Sr |
38 |
87.62 |
g r |
Sulfur |
S |
16 |
32.066(6) |
g r |
Tantalum |
Ta |
73 |
180.95 |
|
Technetium* |
99Tc |
43 |
98.906 |
|
Tellurium |
Te |
52 |
127.60(3) |
g |
Terbium |
Tb |
65 |
158.93 |
|
Thallium |
Tl |
81 |
204.38 |
|
Thorium* |
Th |
90 |
232.04 |
g |
Thulium |
Tm |
69 |
168.93 |
|
Tin (Stannum) |
Sn |
50 |
118.71 |
|
Titanium |
Ti |
22 |
47.867 |
|
Tungsten (Wolfram) |
W |
74 |
183.84 |
|
Ununbium* |
Uub |
112 |
|
|
Ununhexium* |
Uuh |
116 |
|
|
Ununoctium* |
Uuo |
118 |
|
|
Ununpentium* |
Uup |
115 |
|
|
Ununquadium* |
Uuq |
114 |
|
|
Ununtrium* |
Uut |
113 |
|
|
Uranium* |
U |
92 |
238.03 |
g m |
Vanadium |
V |
23 |
50.942 |
|
Xenon |
Xe |
54 |
131.29(2) |
g m |
Ytterbium |
Yb |
70 |
173.04(3) |
g |
Yttrium |
Y |
39 |
88.906 |
|
Zinc |
Zn |
30 |
65.39(2) |
|
Zirconium |
Zr |
40 |
91.224(2) |
g |
†Commercially available Li materials have atomic weights that range between 6.94 and 6.99; if a more accurate value is required, it must be determined for the specific material.
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