Current Table of Standard Atomic Weights in Alphabetical Order
Atomic weights of the elements 2005, Wieser, M. E., Pure Appl. Chem., 78, 2051-2066 (2006). [full text - pdf 217 KB] {TSAW 2005.pdf}
Table of Standard Atomic Weights 2005
[Scaled to Ar(12C) = 12, where 12C is a neutral atom in its nuclear and electronic ground state.]
The atomic weights of many elements are not invariant, but depend on the origin and treatment of the material. The standard values of (E) and the uncertainties (in parentheses, following the last significant figure to which they are attributed) apply to elements of natural terrestrial origin. The footnotes to this table elaborate the types of variation that may occur for individual elements and that may be larger than the listed uncertainties of values of Ar(E). Names of elements with atomic numbers 112 to 118 are provisional.
Alphabetical Order in English |
Name |
Symbol |
Number |
Atomic Weight |
Footnotes |
Actinium* |
Ac |
89 |
|
|
Aluminium (Aluminum) |
Al |
13 |
26.981 538 6(8) |
|
Americium* |
Am |
95 |
|
|
Antimony |
Sb |
51 |
121.760(1) |
g |
Argon |
Ar |
18 |
39.948(1) |
g r |
Arsenic |
As |
33 |
74.921 60(2) |
|
Astatine* |
At |
85 |
|
|
Barium |
Ba |
56 |
137.327(7) |
|
Berkelium* |
Bk |
97 |
|
|
Beryllium |
Be |
4 |
9.012 182(3) |
|
Bismuth |
Bi |
83 |
208.980 40(1) |
|
Bohrium* |
Bh |
107 |
|
|
Boron |
B |
5 |
10.811(7) |
g m r |
Bromine |
Br |
35 |
79.904(1) |
|
Cadmium |
Cd |
48 |
112.411(8) |
g |
Caesium (Cesium) |
Cs |
55 |
132.905 451 9(2) |
|
Calcium |
Ca |
20 |
40.078(4) |
g |
Californium* |
Cf |
98 |
|
|
Carbon |
C |
6 |
12.0107(8) |
g r |
Cerium |
Ce |
58 |
140.116(1) |
g |
Chlorine |
Cl |
17 |
35.453(2) |
g m r |
Chromium |
Cr |
24 |
51.9961(6) |
|
Cobalt |
Co |
27 |
58.933 195(5) |
|
Copper |
Cu |
29 |
63.546(3) |
r |
Curium* |
Cm |
96 |
|
|
Darmstadtium* |
Ds |
110 |
|
|
Dubnium* |
Db |
105 |
|
|
Dysprosium |
Dy |
66 |
162.500(1) |
g |
Einsteinium* |
Es |
99 |
|
|
Erbium |
Er |
68 |
167.259(3) |
g |
Europium |
Eu |
63 |
151.964(1) |
g |
Fermium* |
Fm |
100 |
|
|
Fluorine |
F |
9 |
18.998 4032(5) |
|
Francium* |
Fr |
87 |
|
|
Gadolinium |
Gd |
64 |
157.25(3) |
g |
Gallium |
Ga |
31 |
69.723(1) |
|
Germanium |
Ge |
32 |
72.64(1) |
|
Gold |
Au |
79 |
196.966 569(4) |
|
Hafnium |
Hf |
72 |
178.49(2) |
|
Hassium* |
Hs |
108 |
|
|
Helium |
He |
2 |
4.002 602(2) |
g r |
Holmium |
Ho |
67 |
164.930 32(2) |
|
Hydrogen |
H |
1 |
1.007 94(7) |
g m r |
Indium |
In |
49 |
114.818(3) |
|
Iodine |
I |
53 |
126.904 47(3) |
|
Iridium |
Ir |
77 |
192.217(3) |
|
Iron |
Fe |
26 |
55.845(2) |
|
Krypton |
Kr |
36 |
83.798(2) |
g m |
Lanthanum |
La |
57 |
138.905 47(7) |
g |
Lawrencium* |
Lr |
103 |
|
|
Lead |
Pb |
82 |
207.2(1) |
g r |
Lithium |
Li |
3 |
[6.941(2)]† |
g m r |
Lutetium |
Lu |
71 |
174.967(1) |
g |
Magnesium |
Mg |
12 |
24.3050(6) |
|
Manganese |
Mn |
25 |
54.938 045(5) |
|
Meitnerium* |
Mt |
109 |
|
|
Mendelevium* |
Md |
101 |
|
|
Mercury |
Hg |
80 |
200.59(2) |
|
Molybdenum |
Mo |
42 |
95.94(2) |
g |
Neodymium |
Nd |
60 |
144.242(3) |
g |
Neon |
Ne |
10 |
20.1797(6) |
g m |
Neptunium* |
Np |
93 |
|
|
Nickel |
Ni |
28 |
58.6934(2) |
|
Niobium |
Nb |
41 |
92.906 38(2) |
|
Nitrogen |
N |
7 |
14.0067(2) |
g r |
Nobelium* |
No |
102 |
|
|
Osmium |
Os |
76 |
190.23(3) |
g |
Oxygen |
O |
8 |
15.9994(3) |
g r |
Palladium |
Pd |
46 |
106.42(1) |
g |
Phosphorus |
P |
15 |
30.973 762(2) |
|
Platinum |
Pt |
78 |
195.084(9) |
|
Plutonium* |
Pu |
94 |
|
|
Polonium* |
Po |
84 |
|
|
Potassium |
K |
19 |
39.0983(1) |
|
Praseodymium |
Pr |
59 |
140.907 65(2) |
|
Promethium* |
Pm |
61 |
|
|
Protactinium* |
Pa |
91 |
231.035 88(2) |
|
Radium* |
Ra |
88 |
|
|
Radon* |
Rn |
86 |
|
|
Roentgenium* |
Rg |
111 |
|
|
Rhenium |
Re |
75 |
186.207(1) |
|
Rhodium |
Rh |
45 |
102.905 50(2) |
|
Rubidium |
Rb |
37 |
85.4678(3) |
g |
Ruthenium |
Ru |
44 |
101.07(2) |
g |
Rutherfordium* |
Rf |
104 |
|
|
Samarium |
Sm |
62 |
150.36(2) |
g |
Scandium |
Sc |
21 |
44.955 912(6) |
|
Seaborgium* |
Sg |
106 |
|
|
Selenium |
Se |
34 |
78.96(3) |
r |
Silicon |
Si |
14 |
28.0855(3) |
r |
Silver |
Ag |
47 |
107.8682(2) |
g |
Sodium |
Na |
11 |
22.989 769 28(2) |
|
Strontium |
Sr |
38 |
87.62(1) |
g r |
Sulfur |
S |
16 |
32.065(5) |
g r |
Tantalum |
Ta |
73 |
180.94788(2) |
|
Technetium* |
Tc |
43 |
|
|
Tellurium |
Te |
52 |
127.60(3) |
g |
Terbium |
Tb |
65 |
158.925 35(2) |
|
Thallium |
Tl |
81 |
204.3833(2) |
|
Thorium* |
Th |
90 |
232.038 06(2) |
g |
Thulium |
Tm |
69 |
168.934 21(2) |
|
Tin |
Sn |
50 |
118.710(7) |
g |
Titanium |
Ti |
22 |
47.867(1) |
|
Tungsten |
W |
74 |
183.84(1) |
|
Ununbium* |
Uub |
112 |
|
|
Ununhexium* |
Uuh |
116 |
|
|
Ununoctium* |
Uuo |
118 |
|
|
Ununpentium* |
Uup |
115 |
|
|
Ununquadium* |
Uuq |
114 |
|
|
Ununtrium* |
Uut |
113 |
|
|
Uranium* |
U |
92 |
238.028 91(3) |
g m |
Vanadium |
V |
23 |
50.9415(1) |
|
Xenon |
Xe |
54 |
131.293(6) |
g m |
Ytterbium |
Yb |
70 |
173.04(3) |
g |
Yttrium |
Y |
39 |
88.905 85(2) |
|
Zinc |
Zn |
30 |
65.409(4) |
|
Zirconium |
Zr |
40 |
91.224(2) |
g |
*Element has no stable nuclides. One or more well-known isotopes are given in Table 3 with the appropriate relative atomic mass and half-life. However, three such elements (Th, Pa, and U) do have a characteristic terrestrial isotopic composition, and for these an atomic weight is tabulated.
†Commercially available Li materials have atomic weights that range between 6.939 and 6.996; if a more accurate value is required, it must be determined for the specific material.
g Geological specimens are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such specimens and that given in the table may exceed the stated uncertainty.
m Modified isotopic compositions may be found in commercially available material because it has been subjected to an undisclosed or inadvertent isotopic fractionation. Substantial deviations in atomic weight of the element from that given in the table can occur.
r Range in isotopic composition of normal terrestrial material prevents a more precise Ar(E) being given; the tabulated Ar(E) value should be applicable to any normal material.
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