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Atomic weight
La · lanthanum
란타넘
Takeaway
- Recommended or revised 9 times between 1902 and 2024 (first record 1902, latest revision 2005).
- Both revisions whose previous recommendation had an uncertainty kept the new value inside the previous (expanded) range.
- The current standard atomic weight is 138.905 47(7) (recommended in 2005).
| Yearyear of the recommendation | Value (as printed)as printed in CIAAW's table; digits in parentheses are the uncertainty (expanded range) in the last digits | Notationvalue(uncertainty), interval or no uncertainty | Scalebefore 1961 oxygen = 16, from 1961 ¹²C = 12 | Value, ¹²C scalepre-1961 values multiplied by 15.9994/16 | z vs previous(new − previous) ÷ previous uncertainty | ReportDOI of the CIAAW report |
|---|---|---|---|---|---|---|
| 1902 | 138 | no uncertainty | O=16 | 137.994825 | 10.1007/BF01370337 | |
| 1903 | 138.9 | no uncertainty | O=16 | 138.89479125 | 10.1021/ja02003a001 | |
| 1909 | 139.0 | no uncertainty | O=16 | 138.9947875 | 10.1021/ja01931a001 | |
| 1925 | 138.90 | no uncertainty | O=16 | 138.89479125 | 10.1039/CT9252700913 | |
| 1933 | 138.92 | no uncertainty | O=16 | 138.9147905 | 10.1039/JR9330000354 | |
| 1961 | 138.91 | no uncertainty | 12C=12 | 138.91 | 10.1021/ja00881a001 | |
| 1969 | 138.9055(3) | value(uncertainty) | 12C=12 | 138.9055 | 10.1351/pac197021010091 | |
| 1985 | 138.9055(2) | value(uncertainty) | 12C=12 | 138.9055 | 0.000 | 10.1351/pac198658121677 |
| 2005 | 138.905 47(7) | value(uncertainty) | 12C=12 | 138.90547 | −0.150 | 10.1351/pac200678112051 |
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