About the Periodic Table of Elements
A free, multilingual reference for all 118 chemical elements — what we publish, where the data comes from, and how it is verified.
Last updated: November 1, 2026
Our mission
chem.5l5l.net exists to make accurate chemical reference data easy to read on any device, in any of the ten languages we support. We publish the full periodic table — all 118 named elements — with the physical and atomic properties that students, teachers and working professionals actually look up: atomic number, atomic mass, electron configuration, electronegativity, ionization energy, atomic radius, oxidation states, melting and boiling points, density and year of discovery.
The site is free, requires no account, and is designed to load fast on school computers and mobile connections.
What you will find here
An interactive 18-column periodic table with the lanthanides and actinides shown in their standard positions, colour-coded by element category.
A dedicated page for every element, with the complete property table, an FAQ section written for each element, and links to chemically related elements in the same group and the same period.
Category browsing (alkali metals, noble gases, halogens and so on), full-text search by name, symbol or atomic number, and a machine-readable sitemap and llms.txt file for developers and AI assistants.
Where the data comes from
All physical and atomic properties are transcribed from PubChem, the chemical data repository maintained by the U.S. National Library of Medicine. PubChem data is in the public domain and is the reference used by Wikipedia, PubChem PUG REST and most academic databases, which means the values on this site can be traced back to a primary, citable source.
Element names in the ten supported languages come from Wikidata labels, which are curated by the Wikimedia community. We do not use automated machine translation for element names, because a mistranslated element name is a factual error: an Arabic page that rendered iron (Fe) as copper (Cu) would be actively harmful to a reader. Where a curated label does not exist for a given element and language, we fall back to the English name and mark the page for review rather than publishing a guess.
Element colours follow the conventional CPK palette used in chemistry education.
Editorial standards
Every element page is generated from a single structured record, so the same value cannot appear differently on two pages. The Frequently Asked Questions on each element page are generated from that same record, which means an answer can never contradict the property table above it.
When we find an error, we correct the underlying record and rebuild every affected page, so a fix propagates to all ten languages at once. We do not publish corrections silently: material corrections are noted in the site's change log.
Advertising
This site is supported by advertising, served by Google AdSense. Ads are clearly labelled and kept separate from the reference content. We do not ask anyone to click an ad, do not interfere with the reader's choice of link, and do not run interstitial ads that block the periodic table.
Advertising revenue never influences which elements are listed, what values are shown, or how the site is ranked. Our editorial and advertising policies are managed separately.
Limitations
This is a general reference, not professional advice. Laboratory work, safety decisions and regulatory filings must rely on the primary literature, your institution's own protocols and qualified professionals — not on this website.
Contact
Found a mistake, or want a language added? Write to us and we will look at it.