Credits and licences
Last updated 2026-10-10
Our own code
The tools and page layouts are written for this site. The pages make no requests to other servers.
Third-party material
The worksheet drawings, the PDF writer and all tool code are our own. Element data comes from the source below; we round atomic masses for display and add the common ion charges used in school chemistry.
| Name | Used for | Licence |
|---|---|---|
| PubChem Periodic Table (NCBI, U.S. National Library of Medicine) | Element data for the periodic table and flash cards: atomic mass, electron configuration, electronegativity, state, melting and boiling points, density, year discovered | U.S. government data (public domain); element properties are scientific facts |