Isotopic Abundance & Mass (Accurate)

IsotopeMass (amu)Composition
(atomic %)
H11.00782599.985
H22.01400.015
He33.016030.00014
He44.0026099.99986
Li66.0151217.5
Li77.01600392.5
Be99.012182100
B1010.01293719.8
B1111.00930580.2
C1212.00000098.90
C1313.0033551.10
N1414.00307499.63
N1515.0001080.37
O1615.99491599.762
O1716.9991310.038
O1817.9991600.200
F1918.998403100
Ne2019.99243590.51
Ne2120.9938430.27
Ne2221.9913839.22
Na2322.989767100
Mg2423.98504278.99
Mg2524.98583710.00
Mg2625.98259311.01
Al2726.98154100
Si2827.97692792.23
Si2928.9764954.67
Si3029.9737703.10
P3130.973762100
S3231.97207095.02
S3332.9714560.75
S3433.9678664.21
S3635.9670800.02
Cl3534.96885275.77
Cl3736.96590324.23
Ar3635.9675450.337
Ar3837.9627320.063
Ar4039.96238499.60
K3938.96370793.2581
K4039.9639990.0117
K4140.9618256.7302
Ca4039.96259196.941
Ca4241.9586180.647
Ca4342.9587660.135
Ca4443.9554802.086
Ca4645.9536890.004
Ca4847.9525330.187
Sc4544.955910100
Ti4645.9526298.0
Ti4746.9517647.3
Ti4847.94794773.8
Ti4948.9478715.5
Ti5049.9447925.4
V5049.9471610.25
V5150.94396299.75
Cr5049.9460464.35
Cr5251.94050983.79
Cr5352.9406519.50
Cr5453.9388822.36
Mn5554.938047100
Fe5453.9396125.8
Fe5655.93493991.72
Fe5756.9353962.2
Fe5857.9332770.28
Co5958.933198100
Ni5857.93534668.27
Ni6059.93078826.10
Ni6160.9310581.13
Ni6261.9283463.59
Ni6463.9279680.91
Cu6362.93959869.17
Cu6564.92779330.83
Zn6463.92914548.6
Zn6665.92603427.9
Zn6766.9271294.1
Zn6867.92484618.8
Zn7069.9253250.6
Ga6968.92558060.1
Ga7170.92470039.9
Ge7069.92425020.5
Ge7271.92207927.4
Ge7372.9234637.8
Ge7473.92117736.5
Ge7675.9214017.8
As7574.921594100
Se7473.9224750.9
Se7675.9192129.0
Se7776.9199127.6
Se7877.91730423.5
Se8079.91652049.6
Se8281.9166989.4
Br7978.91833650.69
Br8180.91628949.31
Kr7877.9203970.35
Kr8079.9163802.25
Kr8281.91348211.6
Kr8382.91413511.5
Kr8483.91150757.0
Kr8685.91061617.3
Rb8584.91179472.17
Rb8786.90918727.83
Sr8483.9134300.56
Sr8685.9092679.86
Sr8786.9088847.00
Sr8887.90561982.58
Y8988.905849100
Zr9089.90470351.45
Zr9190.90564411.27
Zr9291.90503917.17
Zr9493.90631417.33
Zr9695.9082752.78
Nb9392.906377100
Mo9291.90608814.84
Mo9493.9050859.25
Mo9594.90584015.92
Mo9695.90467816.68
Mo9796.9060209.55
Mo9897.90540624.13
Mo10099.9074779.63
Tc--
Ru9695.9075995.52
Ru9897.9052871.88
Ru9998.90593912.7
Ru10099.90421912.6
Ru101100.90558217.0
Ru102101.90434831.6
Ru104103.90542418.7
Rh103102.905500100
Pd102101.9056341.02
Pd104103.90402911.14
Pd105104.90507922.33
Pd106105.90347827.33
Pd108107.90389526.46
Pd110109.90516711.72
Ag107106.90509251.84
Ag109108.90475748.16
Cd106105.9064611.25
Cd108107.9041760.89
Cd110109.90300512.49
Cd111110.90418212.80
Cd112111.90275824.13
Cd113112.90440012.22
Cd114113.90335728.73
Cd116115.9047547.49
In113112.9040614.3
In115114.90388095.7
Sn112111.9048261.0
Sn114113.9027840.7
Sn115114.9033480.4
Sn116115.90174714.7
Sn117116.9029567.7
Sn118117.90160924.3
Sn119118.9033108.6
Sn120119.90220032.4
Sn122121.9034404.6
Sn124123.9052745.66
Sb121120.90382157.3
Sb123122.90421642.7
Te120119.9040480.096
Te122121.9030542.60
Te123122.9042710.908
Te124123.9028234.816
Te125124.9044337.14
Te126125.90331418.95
Te128127.90446331.69
Te130129.90622933.80
I127126.904473100
Xe124123.9058940.10
Xe126125.9042810.09
Xe128127.9035311.91
Xe129128.90478026.4
Xe130129.9035094.1
Xe131130.90507221.2
Xe132131.90414426.9
Xe134133.90539510.4
Xe136135.9072148.9
Cs133132.905429100
Ba130129.9062820.106
Ba132131.9050420.101
Ba134133.9044862.417
Ba135134.9056656.592
Ba136135.9045537.854
Ba137136.90581211.23
Ba138137.90523271.70
La138137.9071050.09
La139138.90634699.91
Ce136135.9071400.19
Ce138137.9059850.25
Ce140139.90543388.48
Ce142141.90924111.08
Pr141140.907647100
Nd142141.90771927.13
Nd143142.90981012.18
Nd144143.91008323.80
Nd145144.9125708.30
Nd146145.91311317.19
Nd148147.9168895.76
Nd150149.9208875.64
Pm--
Sm144143.9119983.1
Sm147146.91489515.0
Sm148147.91482011.3
Sm149148.91718113.8
Sm150149.9172737.4
Sm152151.91972926.7
Sm154153.92220622.7
Eu151150.91984747.8
Eu153152.92122552.2
Gd152151.9197860.20
Gd154153.9208612.18
Gd155154.92261814.80
Gd156155.92211820.47
Gd157156.92395615.65
Gd158157.92409924.84
Gd160159.92704921.86
Tb159158.925342100
Dy156155.9252770.06
Dy158157.9244030.10
Dy160159.9251932.34
Dy161160.92693018.9
Dy162161.92679525.5
Dy163162.92872824.9
Dy164163.92917128.2
Ho165164.930319100
Er162161.9287750.14
Er164163.9291981.61
Er166165.93029033.6
Er167166.93204622.95
Er168167.93236826.8
Er170169.93546114.9
Tm169168.934212100
Yb168167.9338940.13
Yb170169.9347593.05
Yb171170.93632314.3
Yb172171.93637821.9
Yb173172.93820816.12
Yb174173.93885931.8
Yb176175.94256412.7
Lu175174.94077097.41
Lu176175.9426792.59
Hf174173.9400440.16
Hf176175.9414065.2
Hf177176.94321718.6
Hf178177.94369627.1
Hf179178.94581213.74
Hf180179.94654535.2
Ta180179.9474620.012
Ta181180.94799299.988
W180179.9467010.13
W182181.94820226.3
W183182.95022014.3
W184183.95092830.67
W186185.95435728.6
Re185184.95295137.40
Re187186.95574462.6
Os184183.9524880.02
Os186185.9538301.58
Os187186.9557411.6
Os188187.95586013.3
Os189188.95813716.1
Os190189.95843626.4
Os192191.96146741.0
Ir191190.96058437.3
Ir193192.96291762.7
Pt190189.9599170.01
Pt192191.9610190.79
Pt194193.96265532.9
Pt195194.96476633.8
Pt196195.96492625.3
Pt198197.9678697.2
Au197196.966543100
Hg196195.9658070.15
Hg198197.96674310.1
Hg199198.96825417
Hg200199.96830023.1
Hg201200.97027713.2
Hg202201.97061729.65
Hg204203.9734676.8
Tl203202.97232029.524
Tl205204.97440170.476
Pb204203.9730201.4
Pb206205.97444024.1
Pb207206.97587222.1
Pb208207.97662752.4
Bi209208.980374100
Po--
At--
Rn--
Fr--
Ra--
Ac--
Th232232.038054100
Pa--
U234234.0409460.0055
U235235.0439240.720
U238238.05078499.2745

Data reprinted from
CRC Handbook of Chemistry and Physics, 69th ed., 1988-89.
Boca Raton, Fl: CRC Press, Inc. &
De Blevre, P, Barnes, IL:
Intl. J. of Mass Spectrometry and Ion Processes. 1985; 65:211- 230.