Repaint the chart
The chart you were shown at school was painted once, by family, and left that way. It does not have to be. Recolour these boxes by any property you like and the same 118 elements rearrange into a different picture every time.
Paint them by how much of the ground is made of them and one box burns brighter than the rest. Paint them by weight and the bottom right corner goes heavy. Paint them by the year they were found and the chart fills up from the middle outwards across two centuries. Search for one by name, or light up every element that holds a record.
The chart
The brightest box under share of the crust is oxygen, at about 46 per cent of the weight of the ground under your feet, locked into rock rather than floating about as air. Under density it is osmium, the heaviest stuff anyone has ever weighed: fill a 600 mL drink bottle with it and you are holding about 13.5 kg, more than a full slab of cans. Under melting point it is carbon, which holds its solid form to about 3,550 °C, close to eight times the heat of a wood-fired pizza oven.
Click or tap a box for its card. Arrow keys walk the chart, Enter opens a card, Escape closes it. On a narrow screen the chart slides sideways inside its own frame.
How to read it
The chart is a seating plan. Every element gets one box, and where that box sits tells you how the atom is put together.
The small number
The number in the corner counts the protons packed into the middle of the atom: one for hydrogen, six for carbon, seventy-nine for gold. That count is the whole identity of an element. Change it and you are holding something else entirely. A kitchen stove cannot get near that, and the reason is a price tag. Chemistry only shuffles the electrons on the outside, at a few electronvolts an atom: an electronvolt is the small shove one electron picks up crossing a one volt gap, about what a torch battery hands out. Shifting the proton count costs millions of electronvolts, roughly a million times steeper a bill, and machines that pay it do the job. Glenn Seaborg's team turned bismuth into gold at Berkeley in 1980, and in 2025 the ALICE experiment at CERN counted lead nuclei shedding three protons to gold as they grazed past each other: about 86 thousand million gold nuclei over one run, close to ten for every person alive, weighing 29 picograms all up. A grain of beach sand runs about a twentieth of a milligram, so the whole haul comes to roughly a two-millionth of one grain.
Reading across
Start top left and read like a page of text: left to right, then drop down. Each new row wraps one more layer of electrons around the middle, so atoms further down the chart are bigger and heavier than the ones above them. The top row holds only two boxes because the first layer has one orbital in it: an orbital is one standing pattern an electron can settle into, and each pattern seats two electrons, one spinning each way. No two electrons in an atom carry the same full description, which is Pauli's rule, and it sets the width of every row below this one as well. Count along the rows and you get 2, 8, 8, 18, 18, 32, 32: the seats each new layer opens up.
Reading down
Now read straight down a column instead. A column is a family: its members tend to carry the same number of electrons out on the rim, so they behave alike. The column running down the left edge holds metals soft enough to cut with a butter knife, once you get past hydrogen at the top. The column down the right edge holds gases that mostly keep to themselves.
The two loose rows
The two rows sitting below the chart belong inside it, at the dashed gaps in rows six and seven. They are lifted out so the whole thing fits on a page. Slot them back where they belong and the chart would be close to twice as wide.
Units on the cards
- °C Degrees Celsius, the everyday scale here. Water freezes at 0 and boils at 100, and a warm summer day on the coast sits near 30. Every temperature on a card leads with this figure.
- K Kelvin, a temperature scale whose zero is the point where a body has given up all the heat it has to give, sitting 273.15 degrees below the freezing point of water. A step of one kelvin is the same size as a step of one degree Celsius, so the two scales differ only in where they start counting. The third law of thermodynamics prices the last step: each halving of the gap costs at least as much work as the halving before it, so laboratories get within billionths of a degree and no further. Ice melts at 0 °C, which is 273 K, and a kettle boils at 100 °C, which is 373 K. Cards carry kelvin in brackets, and lead with it for the handful of elements sitting so close to absolute zero that a Celsius reading stops telling you much.
- g/cm³ What one cubic centimetre weighs, about a sugar cube's worth. Water is 1, so anything under 1 is lighter than water.
- u How heavy one atom is, measured against a carbon atom set at 12.
- pm A picometre: a millionth of a millionth of a metre. A reach from the middle of one atom to the middle of a bonded partner runs a hundred or two of them.
- ppm Parts per million, which works out as grams in a tonne. Ten ppm means ten grams of it in a tonne of rock.
- kJ/mol The energy needed to pull one electron away, counted over a standard batch of atoms rather than a single one.
The families
The starting colours group the boxes into families that behave alike. Here is what each family gets up to, and where you have already met it.
Limits
Figures on a card describe the element in its ordinary form, near room temperature, with gases measured at normal air pressure. Squeeze an element, chill it, or catch it in a different form, and the numbers move. Carbon is the clearest example: at normal air pressure it goes straight from solid to vapour instead of melting, so the melting figure listed for it comes from work done under pressure. Helium is the other way round, staying liquid down to the coldest temperatures unless it is squeezed, so its melting figure comes from pressure too.
A dashed est. tag beside a figure means it was worked out from theory rather than weighed at a bench. Those cluster among the heaviest boxes, where only a handful of atoms have ever existed and each one fell apart in a moment. Nobody has held a gram of hassium to put on a scale.
Crustal shares vary between surveys, since the crust is not the same everywhere you drill. Read them as a good guide to the order of size rather than to the last digit. Sizes on the cards are covalent radii: how far the middle of an atom sits from the middle of a partner it is bonded to. Measure an atom another way and you get a different number for the same element.
Records listed on a card are measured records held under ordinary conditions. Change the conditions and some of them change hands.
Sources
- Periodic Table of the Elements, International Union of Pure and Applied Chemistry · iupac.org/what-we-do/periodic-table-of-elements
- Standard Atomic Weights, IUPAC Commission on Isotopic Abundances and Atomic Weights · ciaaw.org
- Atomic Weights and Isotopic Compositions, National Institute of Standards and Technology · physics.nist.gov/Comp
- CRC Handbook of Chemistry and Physics, CRC Press: physical constants of the elements and crustal abundances
- Half-lives from the National Nuclear Data Center, Brookhaven National Laboratory · nndc.bnl.gov