Standard atomic weights of the elements 2021 (IUPAC Technical Report)

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Abstract

Following the reviews of atomic-weight determinations and other cognate data in 2015, 2017, 2019 and 2021, the IUPAC (International Union of Pure and Applied Chemistry) Commission on Isotopic Abundances and Atomic Weights (CIAAW) reports changes of standard atomic weights. The symbol A _r°(E) was selected for standard atomic weight of an element to distinguish it from the atomic weight of an element E in a specific substance P, designated A _r(E, P). The CIAAW has changed the values of the standard atomic weights of five elements based on recent determinations of terrestrial isotopic abundances:

Ar (argon):	from 39.948 ± 0.001	to	[39.792, 39.963]
Hf (hafnium):	from 178.49 ± 0.02	to	178.486 ± 0.006
Ir (iridium):	from 192.217 ± 0.003	to	192.217 ± 0.002
Pb (lead):	from 207.2 ± 0.1	to	[206.14, 207.94]
Yb (ytterbium):	from 173.054 ± 0.005	to	173.045 ± 0.010

The standard atomic weight of argon and lead have changed to an interval to reflect that the natural variation in isotopic composition exceeds the measurement uncertainty of A _r(Ar) and A _r(Pb) in a specific substance. The standard atomic weights and/or the uncertainties of fourteen elements have been changed based on the Atomic Mass Evaluations 2016 and 2020 accomplished under the auspices of the International Union of Pure and Applied Physics (IUPAP). A _r° of Ho, Tb, Tm and Y were changed in 2017 and again updated in 2021:

Al (aluminium), 2017:	from 26.981 5385 ± 0.000 0007	to	26.981 5384 ± 0.000 0003
Au (gold), 2017:	from 196.966 569 ± 0.000 005	to	196.966 570 ± 0.000 004
Co (cobalt), 2017:	from 58.933 194 ± 0.000 004	to	58.933 194 ± 0.000 003
F (fluorine), 2021:	from 18.998 403 163 ± 0.000 000 006	to	18.998 403 162 ± 0.000 000 005
(Ho (holmium), 2017:	from 164.930 33 ± 0.000 02	to	164.930 328 ± 0.000 007)
Ho (holmium), 2021:	from 164.930 328 ± 0.000 007	to	164.930 329 ± 0.000 005
Mn (manganese), 2017:	from 54.938 044 ± 0.000 003	to	54.938 043 ± 0.000 002
Nb (niobium), 2017:	from 92.906 37 ± 0.000 02	to	92.906 37 ± 0.000 01
Pa (protactinium), 2017:	from 231.035 88 ± 0.000 02	to	231.035 88 ± 0.000 01
Pr (praseodymium), 2017:	from 140.907 66 ± 0.000 02	to	140.907 66 ± 0.000 01
Rh (rhodium), 2017:	from 102.905 50 ± 0.000 02	to	102.905 49 ± 0.000 02
Sc (scandium), 2021:	from 44.955 908 ± 0.000 005	to	44.955 907 ± 0.000 004
(Tb (terbium), 2017:	from 158.925 35 ± 0.000 02	to	158.925 354 ± 0.000 008)
Tb (terbium), 2021:	from 158.925 354 ± 0.000 008	to	158.925 354 ± 0.000 007
(Tm (thulium), 2017:	from 168.934 22 ± 0.000 02	to	168.934 218 ± 0.000 006)
Tm (thulium), 2021:	from 168.934 218 ± 0.000 006	to	168.934 219 ± 0.000 005
(Y (yttrium), 2017:	from 88.905 84 ± 0.000 02	to	88.905 84 ± 0.000 01)
Y (yttrium), 2021:	from 88.905 84 ± 0.000 01	to	88.905 838 ± 0.000 002

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Guidelines and recommended terms for expression of stable-isotope-ratio and gas-ratio measurement results.

Tyler Coplen (2011)

To minimize confusion in the expression of measurement results of stable isotope and gas-ratio measurements, recommendations based on publications of the Commission on Isotopic Abundances and Atomic Weights of the International Union of Pure and Applied Chemistry (IUPAC) are presented. Whenever feasible, entries are consistent with the Système International d'Unités, the SI (known in English as the International System of Units), and the third edition of the International Vocabulary of Basic and General Terms in Metrology (VIM, 3rd edition). The recommendations presented herein are approved by the Commission on Isotopic Abundances and Atomic Weights and are designed to clarify expression of quantities related to measurement of isotope and gas ratios to ensure that quantity equations instead of numerical value equations are used for quantity definitions. Examples of column headings consistent with quantity calculus (also called the algebra of quantities) and examples of various deprecated usages connected with the terms recommended are presented. Published in 2011 by John Wiley & Sons, Ltd.

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Author and article information

Contributors

Philip J. H. Dunn: (View ORCID Profile)

Juris Meija: (View ORCID Profile)

Journal

Title: Pure and Applied Chemistry

Publisher: Walter de Gruyter GmbH

ISSN (Print): 0033-4545

ISSN (Electronic): 1365-3075

Publication date Created: May 25 2022

Publication date Created: March 24 2022

Publication date Created: May 01 2022

Publication date (Print): May 25 2022

Publication date (Electronic): May 04 2022

Publication date (Print): May 01 2022

Volume: 94

Issue: 5

Pages: 573-600

Affiliations

[1 ]Montanuniversität Leoben , Leoben , Austria

[2 ]National Institute of Metrology , Beijing , China

[3 ]University of Natural Resources and Life Sciences Vienna , Tulln , Austria

[4 ]Helmholtz-Zentrum Hereon , Geesthacht , Germany

[5 ]University of Calgary , Calgary , Canada

[6 ]U.S. Geological Survey , Reston , VA , USA

[7 ]PAE, contractor at the Defense POW/MIA Accounting Agency (DPAA) Laboratory , Joint Base Pearl Harbor-Hickam , HI , USA

[8 ]Institute of Mineral Resources, Chinese Academy of Geological Sciences , Beijing , China

[9 ]National Measurement Laboratory, LGC , Teddington , UK

[10 ]Terrestrial Environmental Radiochemistry Laboratory, Department of Nuclear Sciences and Applications , International Atomic Energy Agency , Vienna , Austria

[11 ]National Nuclear Data Center, Brookhaven National Laboratory , Upton , NY , USA

[12 ]Centre for Isotope Research (CIO), University of Groningen , Groningen , The Netherlands

[13 ]Max Planck Institute for Biogeochemistry , Jena , Germany

[14 ]National Institute of Standards and Technology , Gaithersburg , MD , USA

[15 ]The University of Tokyo , Tokyo , Japan

[16 ]Bundesanstalt für Materialforschung und -prüfung (BAM) , Berlin , Germany

[17 ]Department of Chemistry , National University of Singapore , Singapore , Singapore

[18 ]National Museum of Nature and Science , Tokyo , Japan

[19 ]Institute of Geology, Chinese Academy of Geological Sciences , Beijing , China

[20 ]National Research Council of Canada , Ottawa , Canada

Article

DOI: 10.1515/pac-2019-0603

SO-VID: 062d8b78-c087-4c24-bc7e-b8530572998b

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