1.1 Atomic Weights of the Elements (2005)

(This table is taken from www.chem.qmul.ac.uk/iupac/AtWt)

A number in parentheses indicates the uncertainty in the last digit of the atomic weight

List of Elements in Name Order

At No. Symbol Name Atomic Weight 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 Dubinium [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 54.938145(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 [266] 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 Sulphur 32.065(5) 1,2
73 Ta Tantalum 180.94788(2)  
43 Te 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
  1. 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.
  2. Range in isotopic composition of normal terrestrial material prevents a more precise value being given; the tabulated value should be applicable to any normal material.
  3. Modified isotopic compositions may be found in commercially available material because it has been subject to an undisclosed or inadvertent isotopic fractionation. Substantial deviations in atomic weight of the element from that given in the Table can occur.
  4. 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.
  5. Element has no stable nuclides. The value enclosed in brackets, e.g. [209], indicates the mass number of the longest-lived isotope of the element. However, three such elements (Th, Pa, and U) do have a characteristic terrestrial isotopic composition, and for these an atomic weight is tabulated.
  6. The names and symbols for elements 112 – 118 are under review. The temporary system recommended by J Chatt, Pure Appl. Chem., 51, 381-384 (1979) is used above.