Chemistry / Unit 2 Chem 0247 short lesson, about 20 seconds
Standard Atomic Weight Is a Measured, Revisable Value
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The idea
A standard atomic weight is a measured, weighted-average figure that IUPAC's commission reviews and revises as new abundance data arrive.
In practice
Because natural isotopic abundance varies slightly by geographic source, IUPAC lists some elements' weights as an interval, not one fixed number.
Where people slip
A tabulated atomic weight is not a fixed constant of nature — it is a measured figure, open to revision.
Your place on the trail
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