bagleyd AT verizon.net added this to xpt-1.11.0
This version has tvrusso's improvements (most notably "Valence Electrons"
  have been added) to the the original code from Joel P. Lord see
  README.md with work from J. Jansen for OpenVMS.
1. Fixed some annoying warnings and K&R C prototyping.
2. Fixed where each line after Hydrogen was being overlayed slightly by 5
  pixels.
3. I think it looks better using Xaw3d a common variant of Xaw so changed
  the default to that for Unix.
4. Fixed OpenVMS stack dump if clicking twice on help button.  Linux did
  not seem to mind the double XDestroy but fixed there too.

Let me know if you find the data should be updated or if more recently
created elements should be added.