The Periodic Table, With the Stories

Why another periodic table

There is no shortage of periodic tables on the internet, and most of them are one of two things. Either they are an interactive grid that gives you a melting point and a density and then stops, or they are an encyclopaedia article that tells you copper has been used since antiquity but will not tell you what it melts at without a search of its own. The tools and the stories live on different sites, and the calculators live on a third.

That split is inconvenient in a specific, repeated way. A student looking up the electron configuration of iron usually wants to know why 4s fills before 3d in the same sitting. Someone reading about tungsten because of a drill bit wants the melting point and the reason the melting point matters. Splitting those into separate visits serves nobody except the sites collecting the extra pageview.

So this one does all three jobs on the same page: the checked numbers, the written account of what the element actually is and where it turns up, and the calculators next door.

The data has a source, and the source is named

Not one figure on this site is a summary of a summary. Every property, every isotope mass and every abundance can be followed back to the compilation that published it, and the sourcing page does that work for you: which reference supplied what, the day each snapshot was taken, and the six editorial decisions laid over the top of them. That accounting is not decoration. A reference that will not say where its numbers came from is asking to be trusted rather than checked.

Taking that seriously has consequences, and the awkward ones are the interesting ones:

• Fourteen elements have no single atomic weight. The everyday ones first — carbon, oxygen, hydrogen, nitrogen, sulfur and chlorine — then boron, lithium, magnesium, silicon, argon, bromine, thallium and lead. All fourteen vary enough between one natural source and another that IUPAC publishes an interval instead. Their pages print the interval, and say which conventional value the calculators use inside it.
• Thirty-seven elements have no stable isotope at all. For thirty-four of them the weight on the card is a bracketed mass number — the longest-lived isotope, not an average — and the brackets stay put rather than being quietly tidied away. Thorium, protactinium and uranium are the three that escape it: they decay like the rest, but what comes out of the ground is a consistent enough mixture to average, so all three keep a genuine atomic weight.
• Everything above element 103 is largely predicted. A handful of atoms, most of them alive for under a second, do not give you a measured density. Those pages say so at the top of the card.

The calculators show their working

A molar mass of 98.072 and nothing else is not much help to someone whose answer came out at 98.09 and who needs to find out why. So every calculator page lays the intermediate steps out where you can compare them against your own: the per-element breakdown behind a molar mass, the elimination behind a balanced equation, the filling order behind an electron configuration.

The arithmetic underneath is shared by all of them and is unit-tested, and the worked examples on those pages are its actual output rather than a typed-up illustration — if the chemistry library ever got a sum wrong, the page would fail rather than quietly print it. The equation balancer in particular works in exact whole-number fractions rather than floating point, because a balancer that rounds 2.0000000000000004 down to 2 will eventually round something else to the wrong number and never tell you.

Hazards are facts, not instructions

A good many elements are genuinely dangerous, and pretending otherwise would be its own kind of inaccuracy. Where an element is reactive with water, pyrophoric, acutely toxic, carcinogenic or radioactive, its page says so and says what the word means.

What no page here does is tell you what to do with anything. There are no procedures, no preparations, no demonstrations. The hazard block describes a property of a substance in the same register as its boiling point, and stops there.

Built to be read on a phone

The table is eighteen columns wide and always will be, which is a genuine problem on a screen five centimetres across. The compromise here is that the grid scrolls sideways inside its own frame while the page itself never does, and every element also appears in the tapable lists further down, grouped by family and again alphabetically. Nobody should have to pinch and pan to find sodium.

Everything is static HTML with real links. No page queries anything when you open it, so an element arrives as fast as text arrives, and nothing you read here was assembled by a request to somewhere else while you waited. Reading this site sends nothing anywhere.

Where to start

Came for one element? Tap it in the grid above; the fill colour has already told you what family you are about to land in. Came for a calculation? The calculators sit one tap from every page on the site, worked examples and all. Came because a chemistry class stopped making sense somewhere around orbitals? The concept guides begin at the atom and build outward, and none of them assume you followed the last lesson.

Questions the table itself raises

Why does it stop at element 118?

Because that is where confirmed elements stop, not where the physics does. Two laboratories are actively hunting the next one: RIKEN in Japan has been firing a vanadium beam at a curium target since 2018 in pursuit of element 119, and Dubna's Superheavy Element Factory was built to chase 119 and 120 with titanium beams. Neither has produced a claim accepted by the joint IUPAC/IUPAP working party that adjudicates discovery. The day one is accepted, the grid above opens an eighth period and this site gains a page.

Why are two rows printed underneath instead of inside the table?

Typography, not chemistry. The lanthanides and actinides belong in the single-cell gaps you can see in periods 6 and 7, but the f-block is fourteen columns wide, and slotting it in produces a 32-column table roughly twice as wide as the one above. Wide-form tables do exist, and they are arguably the more honest layout; they are also unreadable on anything narrower than a poster. The footnoted form is the compromise every printed table has made since the 1940s.

Why do some symbols look nothing like the element's name?

Eleven of them are abbreviations of a name in another language, usually Latin. Iron is Fe from ferrum, lead is Pb from plumbum, silver is Ag from argentum, potassium is K from kalium and mercury is Hg from hydrargyrum, meaning water-silver. Tungsten is the odd one out: its W comes from wolfram, the German name, which is what most of the world outside English calls the element. Where a symbol and a name disagree like that, the element's own page takes the argument apart.

Why does this site write aluminum and cesium?

Because the compilation the physical properties come from does, and renaming an element away from the table its numbers arrived in is how transcription errors start. IUPAC prefers aluminium and caesium, and its recommended spelling for element 16 has been sulfur rather than sulphur since 1990. Whichever form you type resolves to the same page — the alternative spellings are all wired up, as are the Latin names behind the mismatched symbols — so the choice made here costs a reader nothing beyond a moment's surprise.

How often do these numbers actually change?

Less often than their decimal places suggest. IUPAC's commission revises standard atomic weights on roughly a two-year cycle, and a typical revision nudges a handful of values in their final digit. The changes worth noticing are the rarer structural ones — an element moving to an interval, as argon did in 2017 and lead in 2020, which is a statement that no single value was ever really right. Melting points and densities move rarer still — though not never, and when they do it is usually because someone found a better way to measure rather than a better sample. The densities on the osmium and iridium pages are of that kind, taken from lattice spacings that displaced a much older pair of weighed figures. Absent something like that, a value that has not been revised in fifty years is generally not a neglected one but a settled one.