Rows are shells
Each row — a period — adds one electron shell. Period 1 has room for 2 electrons, period 2 for 8, and so on. A row ends when its outer shell is full, which is why every row finishes with a noble gas.
The periodic table
118 elements, arranged by the rule that gives chemistry its shape. Change the colour channel and a different pattern appears in the same grid.
←↑↓→ move
C compare
/ search
How to read it
Four rules and the whole table makes sense
Columns are behaviour
Each column — a group — shares the same number of outer electrons, and outer electrons are what chemistry is made of. That is why sodium and potassium both detonate in water, and why neon and argon do nothing at all.
Blocks are orbital shapes
The tall columns left and right are the s and p blocks. The wide middle is the d block — the transition metals. The two detached rows are the f block, pulled out only to keep the page a sensible width.
Trends run diagonally
Atoms get smaller and greedier for electrons as you move right and up. Fluorine, at the top right of the reactive elements, is the greediest atom there is; caesium and francium, bottom-left, give their electron away to almost anything.
Common questions
About the periodic table
Why are there exactly 118 elements?
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.
Why are the lanthanides and actinides printed separately?
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.
What does the colour mean?
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.
Which elements are liquid or gas at room temperature?
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.
Where do these numbers come from?
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.