The table includes changes the values for aluminium, bismuth, caesium, cobalt, gold, lanthanum, manganese, neodymium, phosphorus, platinum, samarium, scandium, sodium, tantalum, terbium and thorium. See Pure Appl. Chem. 78, 2051-2066 (2006) for details. Mass number of the longest-lived isotope of hassium from Phys. Rev. Lett., 97 242501 (2006)
https://www.qmul.ac.uk/sbcs/iupac/AtWt/
A PDF of the 2005 table is available.
World Wide Web version of atomic weight data prepared by G. P. Moss, originally from a file provided by D. R. Lide.
Previous values may be consulted from the 1993 table, the 1995 table, the 1997 table the 1999 table or the 2001 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 | 22.98976928(2) | |
12 | Mg | Magnesium | 24.3050(6) | |
13 | Al | Aluminium | 26.9815386(8) | |
14 | Si | Silicon | 28.0855(3) | 2 |
15 | P | Phosphorus | 30.973762(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 | 44.955912(6) | |
22 | Ti | Titanium | 47.867(1) | |
23 | V | Vanadium | 50.9415(1) | |
24 | Cr | Chromium | 51.9961(6) | |
25 | Mn | Manganese | 54.938045(5) | |
26 | Fe | Iron | 55.845(2) | |
27 | Co | Cobalt | 58.933195(5) | |
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 | 132.9054519(2) | |
56 | Ba | Barium | 137.327(7) | |
57 | La | Lanthanum | 138.90547(7) | 1 |
58 | Ce | Cerium | 140.116(1) | 1 |
59 | Pr | Praseodymium | 140.90765(2) | |
60 | Nd | Neodymium | 144.242(3) | 1 |
61 | Pm | Promethium | [145] | 5 |
62 | Sm | Samarium | 150.36(2) | 1 |
63 | Eu | Europium | 151.964(1) | 1 |
64 | Gd | Gadolinium | 157.25(3) | 1 |
65 | Tb | Terbium | 158.92535(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 | 180.94788(2) | |
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 | 195.084(9) | |
79 | Au | Gold | 196.966569(4) | |
80 | Hg | Mercury | 200.59(2) | |
81 | Tl | Thallium | 204.3833(2) | |
82 | Pb | Lead | 207.2(1) | 1, 2 |
83 | Bi | Bismuth | 208.98040(1) | |
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 | 232.03806(2) | 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 | [267] | 5 |
105 | Db | Dubnium | [268] | 5 |
106 | Sg | Seaborgium | [271] | 5 |
107 | Bh | Bohrium | [272] | 5 |
108 | Hs | Hassium | [270] | 5 |
109 | Mt | Meitnerium | [276] | 5 |
110 | Ds | Darmstadtium | [281] | 5 |
111 | Rg | Roentgenium | [280] | 5 |
112 | Uub | Ununbium | [285] | 5, 6 |
113 | Uut | Ununtrium | [284] | 5, 6 |
114 | Uuq | Ununquadium | [289] | 5, 6 |
115 | Uup | Ununpentium | [288] | 5, 6 |
116 | Uuh | Ununhexium | [293] | 5, 6 |
118 | Uuo | Ununoctium | [294] | 5, 6 |
At No | Symbol | Name | Atomic Wt | Notes |
89 | Ac | Actinium | [227] | 5 |
13 | Al | Aluminium | 26.9815386(8) | |
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 | 208.98040(1) | |
107 | Bh | Bohrium | [272] | 5 |
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 | 132.9054519(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 | 58.933195(5) | |
29 | Cu | Copper | 63.546(3) | 2 |
96 | Cm | Curium | [247] | 5 |
110 | Ds | Darmstadtium | [281] | 5 |
105 | Db | Dubnium | [268] | 5 |
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 | 196.966569(4) | |
72 | Hf | Hafnium | 178.49(2) | |
108 | Hs | Hassium | [270] | 5 |
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 | 138.90547(7) | 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 | 54.938045(5) | |
109 | Mt | Meitnerium | [276] | 5 |
101 | Md | Mendelevium | [258] | 5 |
80 | Hg | Mercury | 200.59(2) | |
42 | Mo | Molybdenum | 95.94(2) | 1 |
60 | Nd | Neodymium | 144.242(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 | 30.973762(2) | |
78 | Pt | Platinum | 195.084(9) | |
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 | [280] | 5 |
37 | Rb | Rubidium | 85.4678(3) | 1 |
44 | Ru | Ruthenium | 101.07(2) | 1 |
104 | Rf | Rutherfordium | [267] | 5 |
62 | Sm | Samarium | 150.36(2) | 1 |
21 | Sc | Scandium | 44.955912(6) | |
106 | Sg | Seaborgium | [271] | 5 |
34 | Se | Selenium | 78.96(3) | |
14 | Si | Silicon | 28.0855(3) | 2 |
47 | Ag | Silver | 107.8682(2) | 1 |
11 | Na | Sodium | 22.98976928(2) | |
38 | Sr | Strontium | 87.62(1) | 1, 2 |
16 | S | Sulfur | 32.065(5) | 1, 2 |
73 | Ta | Tantalum | 180.94788(2) | |
43 | Tc | Technetium | [98] | 5 |
52 | Te | Tellurium | 127.60(3) | 1 |
65 | Tb | Terbium | 158.92535(2) | |
81 | Tl | Thallium | 204.3833(2) | |
90 | Th | Thorium | 232.03806(2) | 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 | [293] | 5, 6 |
118 | Uuo | Ununoctium | [294] | 5, 6 |
115 | Uup | Ununpentium | [288] | 5, 6 |
114 | Uuq | Ununquadium | [289] | 5, 6 |
113 | Uut | Ununtrium | [284] | 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 | 65.409(4) | |
40 | Zr | Zirconium | 91.224(2) | 1 |