About
Anyone can find a periodic table in about four seconds. Finding one that will tell you where its figures came from, when they were read, and which of them are genuinely disputed is considerably harder — and a fair number of the values circulating online are predictions that no experiment has ever tested, presented in exactly the same typeface as measurements.
This site exists because that gap is fixable. Every figure here traces back to a named published reference captured on a stated date. Where a figure required a judgement call rather than a lookup — and a handful of them did — the call is set out and argued for on the methodology page instead of being quietly absorbed into the number.
What is actually here
All 118 elements have a page of their own, with the properties on one side and prose on the other that tries to answer why the element matters rather than repeating what the data card already says. Beyond that:
- Family and period hubs for the eleven groupings and the seven rows, covering the trend and the member that breaks it.
- Concept guides aimed at the point where a chemistry class stops making sense — the mole, configurations, oxidation states, balancing — each with worked numbers rather than a definition and a shrug.
- Calculators that run entirely in your browser and print their intermediate steps, because an answer you cannot check against your own working is not much help the night before an exam.
- Comparisons for the twenty pairs people genuinely cross-shop, and short essays on the questions that do not fit anywhere else.
The four rules this site is built on
Every number has a named source. Two published compilations supply the whole dataset — one for isotopes and atomic weights, one for physical and chemical properties — and both are frozen snapshots taken on a stated day rather than lookups performed while you read. What you see today is what was checked.
Uncertainty is printed, not averaged away. Some elements cannot honestly be given one atomic weight; several dozen have nothing stable to report; and the properties of the heaviest are inferred from position rather than measured. All three cases are labelled where they occur instead of being flattened into a confident-looking figure.
Calculators show the arithmetic. Every tool here prints the intermediate steps beside its answer, because the reader who most needs a molar mass is usually the reader who has to reproduce it by hand tomorrow.
Hazards are stated as facts. Toxicity, reactivity and radioactivity are properties of a substance and are reported as such, alongside the specific history that makes each one worth mentioning. What you will not find anywhere is guidance on handling, storing or preparing anything, and that absence is deliberate rather than an oversight. The reasoning behind it is argued out at length under safety and accuracy.
Who runs it
One person: Praveen. Not a laboratory, not an institution, and not a team of contributors whose names would be invented for a credibility page. What stands in for institutional authority here is that everything is checkable — the sources are named, the capture dates are printed, and a disagreement between a number here and a number in a reference you trust can be resolved by looking at both.
These pages sit in a small family of focused reference sites alongside MathQuarry for worked mathematics, ReckonDay for date and duration calculation, GrammarNook for English usage and PantryMetric for kitchen measurement.
Corrections, and how the site pays for itself
If a value here is wrong, the fastest way to fix it is to say so. A reader who names the element and the figure they disagree with saves an hour of guessing, and the contact page sets out what else is worth writing in about.
There is no advertising here. The site is funded by the printable study pack — the same data, typeset for paper — and by readers who choose to chip in. The reference itself is free and stays that way; a chemistry reference behind a paywall would be a worse chemistry reference.