Physical Constants Metrics
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Atomic weight

As · arsenic

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Takeaway
  • Recommended or revised 9 times between 1902 and 2024 (first record 1902, latest revision 2013).
  • All 3 revisions whose previous recommendation had an uncertainty kept the new value inside the previous (expanded) range.
  • The current standard atomic weight is 74.921 595(6) (recommended in 2013).
0+10⁻⁷−10⁻⁷+10⁻⁵−10⁻⁵+10⁻³−10⁻³19001920194019601980200020201961 scale change
Relative deviation from the current (or last) value, symmetric-log axis. Bars: uncertainty (expanded range); open circles: no uncertainty; orange boxes: intervals.
Yearyear of the recommendationValue (as printed)as printed in CIAAW's table; digits in parentheses are the uncertainty (expanded range) in the last digitsNotationvalue(uncertainty), interval or no uncertaintyScalebefore 1961 oxygen = 16, from 1961 ¹²C = 12Value, ¹²C scalepre-1961 values multiplied by 15.9994/16z vs previous(new − previous) ÷ previous uncertaintyReportDOI of the CIAAW report
190275.0no uncertaintyO=1674.997187510.1007/BF01370337
191074.96no uncertaintyO=1674.95718910.1021/ja01919a001
193174.93no uncertaintyO=1674.9271901210.1039/JR9310001617
193474.91no uncertaintyO=1674.9071908810.1039/JR9340000499
196174.9216no uncertainty12C=1274.921610.1021/ja00881a001
196974.9216(1)value(uncertainty)12C=1274.921610.1351/pac197021010091
198574.921 59(2)value(uncertainty)12C=1274.92159−0.10010.1351/pac198658121677
199574.921 60(2)value(uncertainty)12C=1274.92160.50010.1351/pac199668122339
201374.921 595(6)value(uncertainty)12C=1274.921595−0.25010.1515/pac-2015-0305

Source: Standard atomic weights © IUPAC/CIAAW 2016–2024. Commission on Isotopic Abundances and Atomic Weights, Historical changes of standard atomic weights (compiled by J. Meija), https://www.ciaaw.org/historical-atomic-weights.htm