The periodic table

118 is simply how far synthesis has got. Elements up to uranium (92) occur naturally; everything above is assembled by firing nuclei at each other in an accelerator, and each new one is harder to make and shorter-lived than the last. Oganesson (118) completes period 7. Element 119 would open period 8; it has been attempted for years, and so far the nuclei fall apart faster than any detector can register them.

Purely for page width. Chemically they belong inside periods 6 and 7, between groups 2 and 3 — which would make the table 32 columns wide. Almost every printed version pulls them out into a strip below instead. The dashed markers in the main grid show where they actually belong.

Whatever you choose. By default colour shows chemical family — the grouping that best predicts how an element behaves. Switch the colour channel and the same 118 tiles are re-shaded by a measured property, which is the fastest way to see a periodic trend: electronegativity climbs toward the top right, atomic radius grows toward the bottom left, and density peaks in the middle of the transition rows.

At 293 K there are exactly two liquid elements — mercury and bromine — and eleven gases: hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon and radon. Everything else is solid. Set the colour mode to State and drag the temperature slider to watch the boundary move; caesium and gallium melt if you barely warm them, and tungsten is still solid at 3,695 K.

Standard atomic weights follow IUPAC's 2021 table. Physical constants follow the CRC Handbook of Chemistry and Physics and NIST reference data. Values for elements above 100 are largely theoretical predictions — a handful of atoms surviving for milliseconds does not give you a melting point — so where a figure is estimated rather than measured, the element page marks it.