Extensible Periodic Table of Elements

The `periodictable` library for Python (current version 2.1.0) provides an extensible periodic table of elements, pre-populated with data crucial for neutron and X-ray scattering experiments. It offers access to element properties such as mass, density, and scattering information. The library is actively maintained with regular updates to data sources and improvements. Its release cadence is driven by updates to fundamental physical constants and scattering data.