Sources & credits
Affinity is built on published, openly-licensed science. Every empirical value it ships — atomic weights, electronegativities, ionization energies, radii, thermodynamic and equilibrium data, reduction potentials — is taken from one of the sources below and carries its source on the claim itself (thedata / rule-sourced badge). This page is the full public register; the machine-readable one is docs/SOURCES.md in the repository.
Featured content source
by OpenStax, Rice University
Ion charges and the solubility rules; the ΔEN bond-class thresholds; the acid/base and gas-evolution reaction conventions and the oxidation-number rule hierarchy (§4.1–4.2); specific heat capacities (Table 5.1) and standard formation enthalpies (Appendix G); VSEPR electron-domain geometries (§7.6) and the intermolecular-forces boiling-point trend (§10.1); acid, base, and water ionization constants (Appendices H, I, §14.1) and solubility products (Appendix J); rate constants and reaction orders (§12.4); and standard reduction potentials (Appendix L).
This material is used under the Creative Commons Attribution 4.0 International License.Changes were made: Affinity re-derives, re-formats, machine-verifies, and builds original lessons and reference entries on top of these data and conventions. This derivative is not endorsed by OpenStax or Rice University.
Data & reference sources
Standard atomic weights for the 84 elements that have one (abridged 2021 values); a bracketed mass number stands in for the 34 that do not.
Commission on Isotopic Abundances and Atomic Weights, Atomic Weights 2021 report. The values are scientific facts (not copyrightable); © CIAAW covers presentation only.
Element positions (group / period / block) for all 118 elements on the Valence Table, and the longest-lived-isotope mass number for the elements with no standard atomic weight.
International Union of Pure and Applied Chemistry. Definitional structural facts.
The Avogadro, gas, and Faraday constants — each exact by the 2019 SI definitions.
Bureau International des Poids et Mesures. Definitional constants.
First ionization energies for Z = 1–103 (converted from eV to kJ/mol).
National Institute of Standards and Technology — US-government data, public domain. The values are scientific facts.
Normal boiling / sublimation points (H₂O, NH₃, CH₄, CO₂) — the intermolecular-forces evidence.
National Institute of Standards and Technology — US-government data, public domain. The values are scientific facts.
Single-bond covalent radii for the main-group elements through Z = 20.
Cordero, Gómez, Platero-Prats, Revés, Echeverría, Cremades, Barragán & Alvarez, Dalton Trans. 2008, 2832–2838 (doi:10.1039/b801115j). The radii are scientific facts.
The two-decimal revised-Pauling electronegativities (71 elements where an independent cross-check concurs).
A. L. Allred, J. Inorg. Nucl. Chem. 1961, 17 (3–4), 215–221 (doi:10.1016/0022-1902(61)80142-5). The values are scientific facts.
Licensing
Affinity's own content — lesson prose, worked solutions, ledger walkthroughs, Chemical Atlas entries, generated practice, and figures — is released underCC BY-SA 4.0; the code (the ChemKernel producer, the validation gates, and this site) under the MIT License. Empirical data is sourced as registered above — facts are not copyrightable, and each dataset's own license or terms are recorded with it. OpenStax material (CC BY 4.0) is compatible with, and re-shared under, the site's CC BY-SA 4.0 terms.