Fe · iron

철

Takeaway

Recommended or revised 6 times between 1902 and 2024 (first record 1902, latest revision 1993).
The one revision whose previous recommendation had an uncertainty kept the new value inside the previous (expanded) range.
The current standard atomic weight is 55.845(2) (recommended in 1993).

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 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	55.9	no uncertainty	O=16	55.89790375		10.1007/BF01370337
1909	55.85	no uncertainty	O=16	55.84790562		10.1021/ja01931a001
1912	55.84	no uncertainty	O=16	55.837906		10.1021/ja02224a601
1940	55.85	no uncertainty	O=16	55.84790562		10.1039/JR9400000475
1961	55.847(3)	value(uncertainty)	12C=12	55.847		10.1021/ja00881a001
1993	55.845(2)	value(uncertainty)	12C=12	55.845	−0.667	10.1351/pac199466122423

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