Clarifying atomic weights: A 2016 four-figure table of standard and conventional atomic weights
Links
- More information: Publisher Index Page (via DOI)
- Data Releases:
- USGS data release - Four-place table of standard atomic weight values of hydrogen through uranium compared since 1961
- USGS data release - Standard and conventional atomic weights 2016 abridged to four significant digits
- Download citation as: RIS | Dublin Core
Abstract
To indicate that atomic weights of many elements are not constants of nature, in 2009 and 2011 the Commission on Isotopic Abundances and Atomic Weights (CIAAW) of the International Union of Pure and Applied Chemistry (IUPAC) replaced single-value standard atomic weight values with atomic weight intervals for 12 elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, magnesium, silicon, sulfur, chlorine, bromine, and thallium); for example, the standard atomic weight of nitrogen became the interval [14.00643, 14.00728]. CIAAW recognized that some users of atomic weight data only need representative values for these 12 elements, such as for trade and commerce. For this purpose, CIAAW provided conventional atomic weight values, such as 14.007 for nitrogen, and these values can serve in education when a single representative value is needed, such as for molecular weight calculations. Because atomic weight values abridged to four figures are preferred by many educational users and are no longer provided by CIAAW as of 2015, we provide a table containing both standard atomic weight values and conventional atomic weight values abridged to four figures for the chemical elements. A retrospective review of changes in four-digit atomic weights since 1961 indicates that changes in these values are due to more accurate measurements over time or to the recognition of the impact of natural isotopic fractionation in normal terrestrial materials upon atomic weight values of many elements. Use of the unit “u” (unified atomic mass unit on the carbon mass scale) with atomic weight is incorrect because the quantity atomic weight is dimensionless, and the unit “amu” (atomic mass unit on the oxygen scale) is an obsolete term: Both should be avoided.
Publication type | Article |
---|---|
Publication Subtype | Journal Article |
Title | Clarifying atomic weights: A 2016 four-figure table of standard and conventional atomic weights |
Series title | Journal of Chemical Education |
DOI | 10.1021/acs.jchemed.6b00510 |
Volume | 94 |
Issue | 3 |
Year Published | 2017 |
Language | English |
Publisher | ACS Publications |
Contributing office(s) | National Research Program - Eastern Branch |
Description | 9 p. |
First page | 311 |
Last page | 319 |
Google Analytic Metrics | Metrics page |