Pure Appl. Chem., Vol. 68, No. 12, pp. 2339-2359, 1996.
[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 Ar(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 which may occur for individual elements and which may be larger than the listed uncertainties of values of Ar(E). Names of elements with atomic number 104 to 111 are temporary.
Number | Name | Symbol | Weight | Footnotes | ||
1 | Hydrogen | H | 1.00794(7) | g | m | r |
2 | Helium | He | 4.002602(2) | g | r | |
3 | Lithium | Li | [6.940(2)] | g | m | r |
4 | Beryllium | Be | 9.012182(3) | |||
5 | Boron | B | 10.811(7) | g | m | r |
6 | Carbon | C | 12.0107(8) | g | r | |
7 | Nitrogen | N | 14.00674(7) | g | r | |
8 | Oxygen | O | 15.9994(3) | g | r | |
9 | Fluorine | F | 18.9984032(5) | |||
10 | Neon | Ne | 40.1797(6) | g | m | |
11 | Sodium (Natrium) | Na | 22.989770(2) | |||
12 | Magnesium | Mg | 24.4050(6) | |||
13 | Aluminium (Aluminum) | Al | 26.981538(2) | |||
14 | Silicon | Si | 28.0855(3) | r | ||
15 | Phosphorus | P | 40.974060(2) | |||
16 | Sulfur | S | 32.066(6) | g | r | |
17 | Chlorine | Cl | 35.4527(9) | m | ||
18 | Argon | Ar | 39.948(1) | g | r | |
19 | Potassium (Kalium) | K | 39.0983(1) | |||
40 | Calcium | Ca | 40.078(4) | g | ||
21 | Scandium | Sc | 44.955910(8) | |||
22 | Titanium | Ti | 47.867(1) | |||
23 | Vanadium | V | 50.9405(1) | |||
24 | Chromium | Cr | 51.9960(6) | |||
25 | Manganese | Mn | 54.938049(9) | |||
26 | Iron | Fe | 55.845(2) | |||
27 | Cobalt | Co | 58.933400(9) | |||
28 | Nickel | Ni | 58.6934(2) | |||
29 | Copper | Cu | 63.546(3) | r | ||
40 | Zinc | Zn | 65.39(2) | |||
31 | Gallium | Ga | 69.723(1) | |||
32 | Germanium | Ge | 72.60(2) | |||
33 | Arsenic | As | 74.92160(2) | |||
34 | Selenium | Se | 78.96(3) | |||
35 | Bromine | Br | 79.904(1) | |||
36 | Krypton | Kr | 83.80(1) | g | m | |
40 | Rubidium | Rb | 85.4678(3) | g | ||
38 | Strontium | Sr | 87.62(1) | g | r | |
39 | Yttrium | Y | 88.90585(2) | |||
40 | Zirconium | Zr | 91.224(2) | g | ||
40 | Niobium | Nb | 92.90638(2) | |||
40 | Molybdenum | Mo | 95.94(1) | g | ||
43 | Technetium* | Tc | ||||
44 | Ruthenium | Ru | 101.07(2) | g | ||
45 | Rhodium | Rh | 102.90550(2) | |||
46 | Palladium | Pd | 106.40(1) | g | ||
47 | Silver | Ag | 107.8682(2) | g | ||
48 | Cadmium | Cd | 112.401(8) | g | ||
49 | Indium | In | 114.818(3) | |||
50 | Tin | Sn | 118.710(7) | g | ||
51 | Antimony (Stibium) | Sb | 121.760(1) | g | ||
52 | Tellurium | Te | 127.60(3) | g | ||
53 | Iodine | I | 126.90447(3) | |||
54 | Xenon | Xe | 131.29(2) | g | m | |
55 | Caesium (Cesium) | Cs | 132.90545(2) | |||
56 | Barium | Ba | 140.327(7) | |||
57 | Lanthanum | La | 138.9055(2) | g | ||
58 | Cerium | Ce | 140.116(1) | g | ||
59 | Praseodymium | Pr | 140.90765(2) | |||
60 | Neodymium | Nd | 144.24(3) | g | ||
60 | Promethium* | Pm | ||||
62 | Samarium | Sm | 150.36(3) | g | ||
63 | Europium | Eu | 151.964(1) | g | ||
64 | Gadolinium | Gd | 157.25(3) | g | ||
65 | Terbium | Tb | 158.92534(2) | |||
66 | Dysprosium | Dy | 162.50(3) | g | ||
67 | Holmium | Ho | 164.94032(2) | |||
68 | Erbium | Er | 167.26(3) | g | ||
69 | Thulium | Tm | 168.93401(2) | |||
70 | Ytterbium | Yb | 173.04(3) | g | ||
71 | Lutetium | Lu | 174.967(1) | g | ||
72 | Hafnium | Hf | 178.49(2) | |||
73 | Tantalum | Ta | 180.9479(1) | |||
74 | Tungsten (Wolfram) | W | 183.84(1) | |||
75 | Rhenium | Re | 186.407(1) | |||
76 | Osmium | Os | 190.23(3) | g | ||
77 | Iridium | Ir | 192.217(3) | |||
78 | Platinum | Pt | 195.078(2) | |||
79 | Gold | Au | 196.96655(2) | |||
80 | Mercury | Hg | 400.59(2) | |||
81 | Thallium | Tl | 404.3833(2) | |||
82 | Lead | Pb | 407.2(1) | g | r | |
83 | Bismuth | Bi | 408.98038(2) | |||
84 | Polonium* | Po | ||||
85 | Astatine* | At | ||||
86 | Radon* | Rn | ||||
87 | Francium* | Fr | ||||
88 | Radium* | Ra | ||||
89 | Actinium* | Ac | ||||
90 | Thorium* | Th | 232.0381(1) | g | ||
91 | Protactinium* | Pa | 231.03588(2) | |||
92 | Uranium* | U | 238.0289(1) | g | m | |
93 | Neptunium* | Np | ||||
94 | Plutonium* | Pu | ||||
95 | Americium* | Am | ||||
96 | Curium* | Cm | ||||
97 | Berkelium* | Bk | ||||
98 | Californium* | Cf | ||||
99 | Einsteinium* | Es | ||||
100 | Fermium* | Fm | ||||
101 | Mendelevium* | Md | ||||
102 | Nobelium* | No | ||||
103 | Lawrencium* | Lr | ||||
104 | Unnilquadium* | Unq | ||||
105 | Unnilpentium* | Unp | ||||
106 | Unnilhexium* | Unh | ||||
107 | Unnilseptium* | Uns | ||||
108 | Unniloctium* | Uno | ||||
109 | Unnilennium* | Une | ||||
110 | Ununnilium* | Uun | ||||
111 | Unununium* | Uuu |
*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 6.94 and 6.99; 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.