openperiodictable

Understand the periodic table instead of memorizing it. A short course rebuilds the table the way history did, and an app lets you repeat each step.

Open the Periodic Table Builder

The builder, in five steps

  1. Lavoisier, 1789: sort 33 "simple substances" into elements, compounds and non-substances.
  2. Order by atomic weight: the repeating pattern appears.
  3. Mendeleev, 1869: predict a missing element from its neighbours.
  4. Moseley, 1913: the atomic number from X-ray energies.
  5. Electron shells: filling subshells builds all 118 elements.

Course sessions

1. Moseley's law and the atomic number (college level)
Notes (.docx) · Markdown
Square root of K-alpha frequency against atomic number
2. What counts as an element: Lavoisier (college level)
Notes (.docx) · Markdown
What became of Lavoisier's 33 simple substances

Atomic weights in the app are abridged values typed from general knowledge; check them against an IUPAC table before relying on them.

Repository · Back to the main site