Use data from the periodic table at
http://www.ciaaw.org/atomic-weights.htm and
https://iupac.org/wp-content/uploads/2018/12/IUPAC_Periodic_Table-01Dec18.pdf
Elements without any atomic weight in either table do not have a stable
isotope. These are deleted from elements.xml and have their atomic
weight set to -1.0 in Elements.cpp. Add elements after plutonium that
were not previously listed. None of these elements have stable
isotopes.
These elements are retained/added so their symbols, names, and atomic
numbers can still be retrieved and the mapping of atomic number to
index - 1 in the struct is maintained.
Modify the element weight lookup functions to throw errors when an
element with no weight is requested (i.e., the weight is -1.0 in the
struct).
standard states, along with a description of the source for the
values. This was done by Carlos Jove-Colon.
The database is needed to convert gibbs free energies of formation
for each species to species chemical potentials.
