Atomic Masses, Sizes and Abundances

The following information is given in the table below.
1.  Element.  The elements are listed in alphabetical order.  A name in italics means the elemnt is not found naturally on Earth.
2. Z Atomic number
3. A Molar Mass for the naturally occurring isotopic composition to maximum precision so far attained. It is believed that the naturally occurring isotopic composition, and hence the value of A, is constant for each element throughout the Solar System and possibly throughout the Universe.
4. Stable mass numbers and percentage abundances.   Mass numbers of stable nuclides are given in bold type, with the percentage abundance in brackets. A mass number in italics means that the nuclide is radioactive. NR stands for a naturally occurring radionuclide. For radioactive elements only, whether occurring in natural or artificial decay chain, AR stands for the artificial radionuclide, usually that with the longest half-life.
     Element   Symbol    
  Z  

  (g mol-1)    
   
Stable mass numbers and percentage 
Actinium Ac  89  227.0278
227(NR), 228(NR), 226(AR)
Aluminum Al 13 26.9185
27(100)
Americium Am 95 243.06114
243(AR) 
Antimony Sb 51 121.75
121(57.25), 123(42.75)
Argon Ar  18 39.948
36(0.34), 38(0.063), 40(99.6)
Astatine At 85 209.9879
210(AR), 217(AR)
Arsenic As 33 74.9216
75(100)
Barium Ba 56 137.33
130(0.101), 132(0.097), 134(2.42), 135(6.59), 136(7.81), 137(11.32), 138(71.66)
Berkelium Bk 97 247.0703
247(AR)
Beryllium Be 4 9.0122
9(100)
Bismuth Bi 83 208.9804
209(100)
Boron  B 5 10.81
10(19.7), 11(80.3)
Bromine Br 35 79.909
79(50.52), 81(49.48)
Cadmium Cd 48 112.41
106(1.22), 108(0.88), 110(12.39), 111(12.75), 112(24.07), 113(12.26), 114(28.86), 116(7.58)
Cesium Cs 55  132.9504
133(100)
Calcium Ca 20  40.08
40(96.67), 42(0.64), 43(0.15), 44(2.06), 46(0.003), 48(0.19)
Californium Cf 98 252.0817
252(AR)
Carbon C 6 12.0111
12(98.89), 13(1.11), 14(NR)
Cerium Ce 58 140.12
136(0.193), 138(0.23), 140(88.48), 142(11.07)
Chlorine Cl 17 35.453
35(75.73), 37(24.47)
Chromium Cr 24 51.996
50(4.31), 52(83.76), 53(9.55), 54(2.38)
Cobalt Co 27 58.9332
59(100)
Copper Cu 29 63.546
63(69.1), 65(30.9)
Curium Cm 96 247.0704
247(AR)
Deuterium D 1 2.0141

Dysprosium Dy 66 162.50
156(0.05), 158(0.09), 160(2.29), 161(18.88), 162(25.53), 163(24.97), 164(28.18)
Einsteinium Es 99 254.088
254(AR)
Erbium Er 68 167.26
162(0.14), 164(1.56), 166(33.41), 167(22.94), 168(27.07), 170(14.88)
Europium Eu 63 151.96
151(47.77), 153(52.23)
Fermium Fm 100 253.086
253(AR)
Fluorine 9 18.9984
19(100)
Francium Fm 87 223.0198
223(NR), 221(AR)
Gadolinium Gd 64 157.25
152(0.20), 154(2.15), 155(14.7), 156(20.47), 157(15.68), 158(24.9), 160(21.9)
Gallium Ga 31 69.7
69(60.2), 71(39.8)
Germanium Ge 32 72.59
70(20.55), 72(27.37), 73(7.67), 74(36.74), 76(7.67)
Gold Au 79 196.9665
197(100)
Hafnium Hf 72 178.49
174(0.16), 176(5.21), 177(18.56), 178(27.1), 179(13.75), 180(35.22)
Helium He 2 4.0026
3(0.00013), 4(100)
Holmium Ho 67 164.9304
165(100)
Hydrogen H 1 1.0079
1(99.985), 2(0.015), 3(NR)
Indium In 49 114.82
113(4.23), 115(95.77)
Iodine I 53 126.9045
127(100)
Iridium Ir 77 192.22
191(38.5), 193(61.5)
Iron Fe 26 55.847
54(5.84), 56(91.68), 57(2.17), 58(0.31)
Krypton Kr 36 83.80
78(0.35), 80(2.27), 82(11.56), 83(11.55), 84(56.90), 86(17.37)
Lanthanum La 57 138.9055
138(0.09), 139(99.91)
Lawrencium Lr 103 (257)
257(AR)
Lead Pb 82 207.19 
202(0.5), 204(1.40), 206(25.1), 207(21.7), 208(52.3)
Lithium Li 3 6.939
6(7.42), 7(92.58)
Lutetium Lu 71 174.97
175(97.4), 176(2.60)
Magnesium Mg 12 24.312
24(78.60), 25(10.11), 26(11.29)
Manganese Mn 25 54.9380
55(100)
Mendelevium Md 101 257.096
257(AR)
Mercury Hg 80 200.59
196(0.15), 198(10.02), 199(16.84), 200(23.13), 201(13.22), 202(29.80), 204(6.85)
Molybdenum Mo 42 95.49
92(15.86), 94(9.12), 95(15.70), 96(16.50), 97(9.45), 98(23.75), 100(9.62)
Neodymium Nd 60 144.24
142(27.13), 143(12.20), 144(23.87), 145(8.29), 146(17.18), 148(5.72), 150(5.6)
Neon Ne 10 20.18
20(90.92), 21(0.26), 22(8.82)
Neptunium Np 93 239.0530
237(AR),239(AR)
Nickel Ni 28 58.71
58(67.76), 60(26.16), 61(1.25), 62(3.66), 64(1.16)
Niobium Nb 41 92.9064
93(100)
Nitrogen N 7 14.0067
14(99.63), 15(0.37)
Nobelium No 102 255.093
255(AR)
Osmium Os 76 190.2
188(13.3), 189(16.1), 190(26.4), 192(41.0)
Oxygen O 8 15.9994
16(99.759), 17(0.037), 18(0.204)
Palladium Pd 46 106.4
102(1.0), 104(11.0), 105(22.2), 106(27.3), 108(26.7)
Phosphorus P 15 30.9738
31(100)
Platinum Pt 78 195.09
190(0.01), 192(0.78), 194(32.9), 195(33.8), 196(25.2), 198(7.2)
Plutonium Pu 94 239.0522
238(AR), 239(AR), 242(AR)
Polonium Po 84 210.0000
210(NR)
Potassium K 19 39.0983
39(93.22), 40(0.12), 41(6.77)
Praeosdymium Pr 59 140.9077
141(100)
Promethium Pm 61 144.9126
145(AR)
Protactinium Pa 91 231.0359
231(NR), 233(AR), 234(NR)
Radium Ra 88 226.0254
226(NR), 228(NR), 224(NR), 223(NR)
Radon Rn 86 222.0176
222(NR), 220(NR)
Rhenium Re 75 186.207
185(37.07), 187(62.93)
Rhodium Rh 45 102.9055
103(100)
Rubidium Rb 37 85.468
85(72.15), 87(27.85)
Terbium Tb 65 158.9254
159(100)
Ruthenium Ru 44 101.07
96(5.46), 98(1.87), 99(12.53), 101(17.02), 102(31.60), 104(18.87)
Samarium Sm 62 150.35
144(3.16), 147(15.07), 148(11.27), 49(13.82), 150(7.47), 152(26.63), 154(22.53)
Scandium Sc 21 44.9559
45(100)
Selenium Se 34 78.96
74(0.89), 76(9.02), 77(7.58), 78(23.52), 80(49.82), 82(9.19)
Silicon Si 14 28.0855
28(92.18), 29(4.71), 30(3.12)
Silver Ag 47 107.868
107(51.35), 109(48.65)
Sodium Na 11 22.9898
23(100) 
Strontium Sr 38 87.62
84(0.56), 86(9.86), 87(7.02), 88(82.56)
Sulphur S 16 32.06
32(95), 33(0.76), 34(4.22), 36(0.01)
Tantalum Ta 73 180.9479
180(0.01), 181(99.99)
Technetium Tc 43 98.9062
99(AR)
Tellurium Te 52 127.60
120(0.09), 122(2.46), 123(0.87), 124(4.61), 125(6.99), 126(18.71), 128(31.79), 130(34.49)
Thallium Tl 81 204.37
203(29.5), 205(70.5)
Thorium Th 90 232.038
232(NR)
Thulium Tm 69 168.9342
169(100)
Tin Sn 50 118.69
112(0.95), 114(0.65), 115(0.34), 116(14.24), 117(7.57), 118(24.01), 119(8.58), 120(32.97), 122(4.71), 124(5.98)
Titanium Ti 22 47.90
46(7.99), 47(7.32), 48(73.99), 49(5.46), 50(5.25)
Tungsten W 74 183.85
180(0.14), 182(26.4), 183(14.4), 184(30.6), 186(28.4)
Tritium T 1 3.0161
3(NR and AR)
Uranium U 92 238.029
234(0.0057), 235(0.7196), 238(99.276)
Vanadium V 23 50.9415
50(0.25), 51(99.75)
Xenon Xe 54 131.30
124(0.013), 126(0.09), 128(1.92), 129(26.44), 130(4.08), 131(21.18),  132(26.89), 134(10.4), 136(8.87)
Ytterbium Yb 70 173.04
168(0.14), 170(3.03), 171(14.31), 172(21.82), 173(16.13), 174(31.84), 176(12.73)
Yttrium Y 39 88.9059
89(100)
Zinc Zn 30 65.38
64(48.89), 66(27.81), 67(4.11), 68(18.56), 70(0.62)
Zirconium Zr 40 91.22
90(51.46), 91(11.23), 92(17.11),  94(17.40), 96(2.80)