Atomic weights slightly wrong

[NicholasWMRitchie]

I believe the source of the atomic weight data is the IUPAC 2021 tabulation. However, there is a subtle misinterpretation of the data in this table that plays through to the values of the atomic weights in PeriodicTable.jl.

The reported uncertainty in the atomic weight column is being interpreted incorrectly.

In PeriodicTable.jl, the atomic weight of Ne is reported as 20.17976u. In the IUPAC table, it is listed as 20.1797(6). 20.1797(6) does not mean 20.17976. It means $20.1797 \pm 0.0006$. Similarly, Yb has an atomic weight of 173.045(10) or $173.045 \pm 0.010$.

The correct interpretation of the parenthesis at the end is to assume this amount of uncertainty in the final digits of the preceding number.

This error is repeated for all elements with reported uncertainties on the atomic weights.

[NicholasWMRitchie]

I see that this has been previously reported.

[carstenbauer]

Thanks for the issue. Would be great if you could prepare a PR that fixes this for all elements.

[NicholasWMRitchie]

@carstenbauer Done. 😃