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Atomic Weights & Isotopic Compositions
with Relative Atomic Masses

Developers and Contributors:
J. S. Coursey, D. J. Schwab, J. J. Tsai, and R. A. Dragoset

NIST Physical Measurement Laboratory

The atomic weights are available for elements 1 through 118 and isotopic compositions or abundances are given when appropriate. The atomic weights data were published by J. Meija et al in Atomic Weights of the Elements 2013, and the isotopic compositions data were published by M. Berglund and M.E. Wieser in Isotopic Compositions of the Elements 2009. The relative atomic masses of the isotopes data were published by M. Wang, G. Audi, A.H. Wapstra, F.G. Kondev, M. MacCormick, X. Xu1, and B. Pfeiffer in The AME2012 Atomic Mass Evaluation.

These data have been compiled from the above sources for the user's convenience and does not represent a critical evaluation by the NIST Physical Measurement Laboratory.

isotopic compositions link
link to iupac link to csnsm

Development of this database was funded in part by NIST's Systems Integration for Manufacturing Applications (SIMA) Program.

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All Elements
  HTML Table
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  Most common isotopes
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NIST Standard Reference Database 144
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Online: September 1999  -  Last update: January 2015


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