CIAAW

Standard and abridged atomic weights, isotopic abundances and nuclides’ standard atomic weights according to CIAAW.

SAW: Standard Atomic Weights

The latest standard atomic weights were released in 2021 by the [ciaaw](https://www.ciaaw.org). All the values for the atomic weights are provided as double precision reals.

The standard atomic weights (or realtive atomic mass),:math:A_r(E), are extracted from table 1 from Prohaska et al. [1]. For the elements that feature an interval for the standard atomic weight, the mean value and the uncertainty are computed using formulas defined in [2].

\[ \begin{align}\begin{aligned}A_r(E) = \frac{a+b}{2}\\u(A_r(E)) = \frac{b-a}{2\sqrt{3}}\end{aligned}\end{align} \]

The standard atomic weights are a dimensionless quantity and thus they need to be multiplied by the molar mass constant \(M_u=1.00000000105 \pm 0.00000000031 g.mol^{-1}\) in order to get the value in \(g.mol^{-1}\). See codata for physical constants.

ICE: Isotopic Compositions of the Element

The latest isotopic compositions were released in 2013 by the [ciaaw](https://www.ciaaw.org). All the values for the compositions are provided as double precision reals. The isotopic compositions of the element, are extracted from table 1 from Meija et al. [3].

NAW: Nuclide Atomic Weights

The latest atomic weights for nuclides were released in 2020 by [ciaaw](https://www.ciaaw.org) from Huang et al. [4]. All the values for the nuclide atomic weights are provided as double precision reals.