Johanna Irrgeher
Jacqueline Benefield
J.K. Bohlke
Lesley Chesson
Tyler B. Coplen
Tiping Ding
Philip J.H. Dunn
Manfred Groning
Norman E. Holden
Harro A. J. Meijer
Heiko Moossen
Antonio Possolo
Yoshio Takahashi
Jochen Vogl
Thomas Walczyk
Jun Wang
Michael E. Wieser
Shigekazu Yoneda
Xiang-Kun Zhu
Juris Meija
Thomas Prohaska
2022
<p>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<span> </span><i>A</i><span> </span><sub>r</sub>°(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<span> </span><i>A</i><span> </span><sub>r</sub>(E, P). The CIAAW has changed the values of the standard atomic weights of five elements based on recent determinations of terrestrial isotopic abundances:</p><p><br></p><div id="j_pac-2019-0603_tab_101" class="table-wrap"><table class="content-table mce-item-table" border="0" frame="hsides" rules="groups"><colgroup><col align="left"><col align="left"><col align="left"><col align="left"></colgroup><tbody><tr><td>Ar (argon):</td><td>from 39.948 ± 0.001</td><td>to</td><td>[39.792, 39.963]</td></tr><tr><td>Hf (hafnium):</td><td>from 178.49 ± 0.02</td><td>to</td><td>178.486 ± 0.006</td></tr><tr><td>Ir (iridium):</td><td>from 192.217 ± 0.003</td><td>to</td><td>192.217 ± 0.002</td></tr><tr><td>Pb (lead):</td><td>from 207.2 ± 0.1</td><td>to</td><td>[206.14, 207.94]</td></tr><tr><td>Yb (ytterbium):</td><td>from 173.054 ± 0.005</td><td>to</td><td>173.045 ± 0.010</td></tr></tbody></table></div><p><br></p><p>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<span> </span><i>A</i><span> </span><sub>r</sub>(Ar) and<span> </span><i>A</i><span> </span><sub>r</sub>(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).<span> </span><i>A</i><span> </span><sub>r</sub>° of Ho, Tb, Tm and Y were changed in 2017 and again updated in 2021:</p><p><br></p><div id="j_pac-2019-0603_tab_102" class="table-wrap"><table class="content-table mce-item-table" border="0" frame="hsides" rules="groups"><colgroup><col align="left"><col align="left"><col align="left"><col align="left"></colgroup><tbody><tr><td>Al (aluminium), 2017:</td><td>from 26.981 5385 ± 0.000 0007</td><td>to</td><td>26.981 5384 ± 0.000 0003</td></tr><tr><td>Au (gold), 2017:</td><td>from 196.966 569 ± 0.000 005</td><td>to</td><td>196.966 570 ± 0.000 004</td></tr><tr><td>Co (cobalt), 2017:</td><td>from 58.933 194 ± 0.000 004</td><td>to</td><td>58.933 194 ± 0.000 003</td></tr><tr><td>F (fluorine), 2021:</td><td>from 18.998 403 163 ± 0.000 000 006</td><td>to</td><td>18.998 403 162 ± 0.000 000 005</td></tr><tr><td>(Ho (holmium), 2017:</td><td>from 164.930 33 ± 0.000 02</td><td>to</td><td>164.930 328 ± 0.000 007)</td></tr><tr><td>Ho (holmium), 2021:</td><td>from 164.930 328 ± 0.000 007</td><td>to</td><td>164.930 329 ± 0.000 005</td></tr><tr><td>Mn (manganese), 2017:</td><td>from 54.938 044 ± 0.000 003</td><td>to</td><td>54.938 043 ± 0.000 002</td></tr><tr><td>Nb (niobium), 2017:</td><td>from 92.906 37 ± 0.000 02</td><td>to</td><td>92.906 37 ± 0.000 01</td></tr><tr><td>Pa (protactinium), 2017:</td><td>from 231.035 88 ± 0.000 02</td><td>to</td><td>231.035 88 ± 0.000 01</td></tr><tr><td>Pr (praseodymium), 2017:</td><td>from 140.907 66 ± 0.000 02</td><td>to</td><td>140.907 66 ± 0.000 01</td></tr><tr><td>Rh (rhodium), 2017:</td><td>from 102.905 50 ± 0.000 02</td><td>to</td><td>102.905 49 ± 0.000 02</td></tr><tr><td>Sc (scandium), 2021:</td><td>from 44.955 908 ± 0.000 005</td><td>to</td><td>44.955 907 ± 0.000 004</td></tr><tr><td>(Tb (terbium), 2017:</td><td>from 158.925 35 ± 0.000 02</td><td>to</td><td>158.925 354 ± 0.000 008)</td></tr><tr><td>Tb (terbium), 2021:</td><td>from 158.925 354 ± 0.000 008</td><td>to</td><td>158.925 354 ± 0.000 007</td></tr><tr><td>(Tm (thulium), 2017:</td><td>from 168.934 22 ± 0.000 02</td><td>to</td><td>168.934 218 ± 0.000 006)</td></tr><tr><td>Tm (thulium), 2021:</td><td>from 168.934 218 ± 0.000 006</td><td>to</td><td>168.934 219 ± 0.000 005</td></tr><tr><td>(Y (yttrium), 2017:</td><td>from 88.905 84 ± 0.000 02</td><td>to</td><td>88.905 84 ± 0.000 01)</td></tr><tr><td>Y (yttrium), 2021:</td><td>from 88.905 84 ± 0.000 01</td><td>to</td><td>88.905 838 ± 0.000 002</td></tr></tbody></table></div>
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10.1515/pac-2019-0603
en
De Gruyter
Standard atomic weights of the elements 2021 (IUPAC Technical Report)
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