Nuclide Chart

Trends across the whole chart of nuclides, built on real data from the IAEA Live Chart of Nuclides (ENSDF, NUBASE2020, AME2020). Most of nuclear physics only shows up when many nuclides are compared, so students find it themselves:

• Ni-62, not Fe-56, is the most tightly bound nuclide.
• The magic numbers appear as bumps in the mass-formula residuals and as cliffs in the separation energies.
• Isobars lie on mass parabolas.
• Half-lives span more than 50 orders of magnitude, and α half-lives fall on Geiger–Nuttall lines.
• Every decay series reaches secular equilibrium.

It is written for introductory modern physics (the nuclear chapter of the QuadriviumPress Modern Physics textbook). Built with SceneryStack; runs offline as a Progressive Web App.

Features

• Chart.
  • Every known ground state (3,386) on an N–Z map that pans, zooms and selects.
  • Colour by decay mode, half-life, B/A, mass-formula residual, natural abundance, measured or estimated mass, quadrupole moment, or spin.
  • Overlays: magic numbers, N = Z, the valley of stability and the drip lines.
  • A half-life filter starting at the age of the Earth answers "why do some radioactive nuclides still exist?".
  • A Q-value predictor: students work each Q out from the mass excesses, then reveal the answers. Each decay is shown as allowed and observed, allowed but not observed, or forbidden.
  • A census of stable nuclides by the parity of Z and N, with two definitions of "stable".
• Binding Energy.
  • The B/A curve with a zoom on its peak, where Ni-62 beats Fe-58 and Fe-56.
  • The semi-empirical mass formula: switch terms off, move the coefficients, fit them to the measured masses, or go back to the textbook values.
  • Residuals (measured − formula) against N or Z show the shell closures.
  • Energy released by U-235 fission, from the curve (≈ 0.9 MeV × 235) and from the masses (≈ 200 MeV).
  • Nine fusion reactions, from D–T to Fe-56 + α.
• Shells.
  • S₂ₙ, Sₙ, S₂ₚ or Sₚ, one line per element or per isotone.
  • The line of the selected nuclide is highlighted, with its drop to the next nuclide.
  • The unbound region is shaded.
• Isobars.
  • The mass excess of one A's isobars against Z.
  • Fitted mass parabolas: one for odd A, two for even A.
  • Arrows for every allowed β⁻, β⁺/EC and double-β step.
  • The β-stable isobars and Mattauch's rule. Ge-76, Te-130 and Xe-136 decay only by double β.
• Half-Lives.
  • Every measured half-life against A or against distance from the valley, on log or linear scales.
  • Guides at one second, one year, the age of the Earth and the age of the Universe.
  • The Geiger–Nuttall lines of even–even α emitters (Po-212 against Th-232: 24 orders of magnitude).
  • Sargent's rule for β⁻ emitters.
• Decay Chains.
  • The four natural series (4n, 4n+1, 4n+2, 4n+3) traced from the data on their patch of the chart.
  • Each member's activity over time from the exact Bateman solution, rising to secular equilibrium.
  • The Pb/U ratio as a dating clock.
  • Fission products: the two-humped yield curve for U-235, Pu-239 and U-238, and the β⁻ chain along any A, with delayed-neutron emitters flagged.
• Real data, offline.
  • The IAEA API cannot be queried from a web page, so the sim bundles a snapshot (about 600 KB). npm run fetch-data refreshes it.
  • Q values, separation energies, chains and fits are computed in the sim from the masses and decay branches, and tested against the IAEA's own values.
• Accessible.
  • Every chart can be used from the keyboard.
  • Each screen has a live screen summary and a keyboard-help dialog.
  • Default and projector colour profiles.
  • English, French and Spanish.
  • Installable PWA.

Quick Start

npm install
npm start        # dev server → http://localhost:5173

Scripts

Command	Description
npm start / npm run dev	Start Vite dev server
npm run build	Type-check + production build → dist/
npm run preview	Preview the production build locally
npm test	Run Vitest unit tests (includes memory-leak suite)
npm run test:fuzz	Optional Playwright fuzz smoke: pointer (?fuzz) + keyboard (?fuzzBoard), with ?ea, 30s each
npm run test:fuzz -- 90	Same fuzz for 90 seconds (--duration 90 or FUZZ_DURATION=90 also work)
npm run test:fuzz:quick	Shorter fuzz smoke (10s)
npm run test:fuzz:long	Longer fuzz smoke (300s)
npm run check	TypeScript type check
npm run lint	Biome lint check
npm run format	Auto-format all files
npm run fix	Lint + auto-fix
npm run icons	Regenerate PNG icons from public/icons/icon.svg
npm run fetch-data	Take a new snapshot of the IAEA Live Chart of Nuclides (needs network)
npm run release	check && lint && build && test, then version patch + push tags
npm run clean	Remove dist/

The snapshot is frozen on purpose so that class answers stay put during a term. To refresh it:

1. Run npm run fetch-data.
2. Check the summary it prints (about 3,400 ground states, and fission yields summing to 2 per fission).
3. Run the tests.
4. Commit src/common/model/data/.

Tech Stack

Tool	Version	Purpose
SceneryStack	^3.0.0	Simulation framework
Vite	^8	Build tool + dev server
TypeScript	^7	Type-safe JavaScript
Biome	^2.6	Linting + formatting
vite-plugin-pwa	^2	PWA + service worker

License

GNU Affero General Public License v3.0 — see OpenLyceum org license. The bundled nuclear data come from the IAEA Nuclear Data Section, under its own terms. See CREDITS.md for the acknowledgements.

Contributing

See OpenLyceum contributing guidelines. Report bugs via GitHub Issues; use org issue templates.