Atomic masses misinterpreted

[zhaiyusci]

Dear developers,

I happen to find that you may have some misinterpreted atomic masses raw data.

I know that the data is from this repo. Maybe I should also address an issue there. But let me speak here first, as we have Measurements.jl by the same Organization.

Atomic weights provided by IUPAC, which is the data source of Wikipedia, are given in two formats. The first one is [x, y], means the measured value is between x and y, the second one is d.dd(e), means the measured value is d.dd, with standard deviation of 0.0e, or in short, measurement("d.dd(e)") if we use the Measurements.jl package.

However, PeriodicTable.jl gives

julia> elements[:He].atomic_mass
4.0026022 u

While the raw data from IUPAC is 4.002602(2). Apparently, when compile the data for PeriodicTable.jl, the error between parentheses is taken as the last decimal of the mean value, which means the value given by this package is always greater than that by IUPAC.

Hope we can fix it.

Cheers, Yu

[NicholasWMRitchie]

@zhaiyusci See pull request #57. 😃

[NicholasWMRitchie]

Resolved.