The Periodic Table: Chemistry's Map
118 elements, one chart — and once you see how it's sorted, you can predict chemistry you've never been taught.
Builds on: 0.1 Atoms: The Alphabet of Matter0.2 Electron Shells: Where Electrons Live
Not a list — a map
In 1869 Dmitri Mendeleev sorted the known elements by weight and noticed properties repeating in waves — so he stacked the waves. The result is the periodic table: elements ordered by atomic number Z, arranged so that columns share chemistry. It was such a good map that Mendeleev left gaps and predicted the missing elements’ properties — gallium and germanium showed up years later, matching his guesses almost exactly.
Rows are shells, columns are valence
With Unit 0 behind you, the table’s layout is no longer arbitrary. Each row (period) corresponds to one electron shell being filled: period 1 fills the 2-slot first shell (2 elements), periods 2 and 3 fill 8-slot shells (8 elements each). Each column (group) collects elements with the same number of valence electrons — and since valence electrons are an element’s chemistry, columns behave like families:
- Group 1 — alkali metals (Li, Na, K…): one lonely outer electron, desperate to lose it. Soft metals that hiss, fizz or explode in water.
- Group 2 — alkaline earth metals (Mg, Ca…): two outer electrons, still eager to shed them — just less dramatically.
- Group 17 — halogens (F, Cl, Br, I): one electron short of a full shell, aggressive electron thieves. Fluorine is the most reactive element known.
- Group 18 — noble gases (He, Ne, Ar…): full shells, chemically asleep.
- The wide middle block — transition metals — and the two detached rows below (lanthanides and actinides) fill inner floors of the electron hotel; they are the table’s more intricate districts.
The symbols are international, but their roots are Latin and Greek: iron is Fe (ferrum), sodium is Na (natrium), potassium is K (kalium), tungsten is W (German Wolfram!). No one guesses these — everyone memorizes them. That’s exactly what an Eselsbrücke (German for “donkey bridge” — a mnemonic) is for: a little story that carries you from the name to the symbol. Every element in the lab below has one.
Trends you can read off the map
Two rules of thumb cover most of the table. Moving left → right across a period, the nucleus gains charge and pulls electrons in tighter: atoms get smaller and hold electrons more greedily. Moving top → bottom down a group, new shells stack on: atoms get bigger and their outer electrons easier to steal. That is why the most violent metal (caesium, bottom-left) and the most violent non-metal (fluorine, top-right) live in opposite corners.
⚗️ Lab — The Periodic Table — with an Eselsbrücke for Every Element
The full map, 118 tiles. Click any element for its data and its Eselsbrücke — the German memory hook linking its name to its symbol. (The standalone page under 🧪 Elements in the top bar adds a searchable list view.)
- Walk down group 1, then across period 3 — watch the categories change color.
- Find the four elements named after the village of Ytterby (Y, Tb, Er, Yb).
- Check the “deceptive” symbols: Na, K, Fe, Sn, Pb, Ag, Au, W, Hg.
Click an element in the table to see its details and Eselsbrücke.