The data set contains the atomic weights of the elements and their isotopes.
It is used to calculate the exact mass in formula_to_mass but can also be used as a reference.
description
Format
atoms
A data frame with 442 rows and 7 columns:
- Number
The atomic number of the element in the periodic table.
- Element
The element.
- Isotope
The mass number of the specific isotope.
- Symbol
The atomic symbol. Either only the letter (for standard isotopes) or the mass number followed by the symbol (for special isotopes).
- Weight
The monoisotopic mass of the isotope.
- Composition
The fraction of the isotope in the naturally occuring element.
- Standard_Weight
The standard atomic weight of the element. It is the sum of the product of the
WeightandCompositioncolumn for each element. Where no composition is available, the weight of the IUPAC "ATOMIC WEIGHTS OF THE ELEMENTS 2023" table was used. See the Source section for more information.
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Source
The table was retrieved from the National Institute of Standards and Technology (NIST) at https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl, accesed in October 2025, and enriched with data from the IUPAC "ATOMIC WEIGHTS OF THE ELEMENTS 2023" table at https://iupac.qmul.ac.uk/AtWt/, accesed in October 2025