Extensible periodic table of the elements (Python 3)

 This package provides a periodic table of the elements with support
 for mass, density and xray/neutron scattering information.
 .
 Masses, densities and natural abundances come from the NIST Physics
 Laboratory, but do not represent a critical evaluation by NIST
 scientists.
 .
 Neutron scattering calculations use values collected by the Atomic
 Institute of the Austrian Universities. These values do corresponding
 to those from other packages, though there are some differences
 depending to the tables used. Bound coherent neutron scattering for
 gold in particular is significantly different from older value:
 7.63(6) as measured in 1974 compared to 7.90(7) as measured in 1990.
 .
 X-ray scattering calculations use a combination of empirical and
 theoretical values from the LBL Center for X-ray Optics. These values
 differ from those given in other sources such as the International
 Tables for Crystallography, Volume C, and so may give different
 results from other packages.
 .
 This package installs the library for Python 3.