# Periodic Table of the Elements > Interactive periodic table with detailed information for all 118 chemical elements. Available in English, Swedish, Danish and Spanish. Each element page covers physical properties (atomic mass, density, melting/boiling point), atomic structure (electron configuration, shells, orbital diagram), classification (category, period, block, group), discovery history (who, when, naming origin), and external identifiers (CAS Number, ChemSpider ID, EC number, PubChem CID). The site also hosts six free interactive quizzes for memorising symbols, atomic numbers, categories and table layout. Data is sourced from Wikipedia with attribution on each element page. Structured data is exposed via JSON-LD in every page's `` for direct machine consumption. ## Machine-readable data - [JSON API](https://www.periodictable.one/api/elements.json): all 118 elements with full data (physical properties, atomic structure, identifiers, discovery history, translations in all active languages). One single endpoint, no pagination, ~80 KB. Cached 1 hour. CORS-enabled. - [Search API](https://www.periodictable.one/api/search.json?q=gold): typeahead lookup by name or symbol, JSON response. ## Sitemap - [XML sitemap](https://www.periodictable.one/sitemap.xml): all URLs with `hreflang` alternates per language. Covers element pages, comparison pages, properties, history and the full quiz section. ## Core pages (English) - [Home / Periodic table](https://www.periodictable.one/): interactive grid of all 118 elements - [Chemical elements](https://www.periodictable.one/elements): all 118 elements with a stats banner, four view modes (Cards default, Compact mini-cards, sortable Table, alphabetical 3-column List), chip-style category filters, and a "Browse by" section linking the other filter dimensions. 41 filter sub-pages in total: nine categories (`/elements/nonmetals`, `/noble-gases`, `/alkali-metals`, `/alkaline-earth-metals`, `/metalloids`, `/post-transition-metals`, `/transition-metals`, `/lanthanides`, `/actinides`), three phases (`/elements/solid`, `/liquid`, `/gas`), seven periods (`/elements/period/1` … `/period/7`), eighteen groups (`/elements/group/1` … `/group/18`), and four blocks (`/elements/block/s`, `/p`, `/d`, `/f`). Each sub-page is its own indexable list with a heading, intro paragraph and the same four view modes. - [Element detail](https://www.periodictable.one/element/1): full data for one element (replace `1` with any atomic number 1-118) - [Compare elements](https://www.periodictable.one/compare): side-by-side comparison of two elements (URL pattern: `/compare/{element1}-vs-{element2}`) - [Periodic table history](https://www.periodictable.one/history): timeline of discoveries, discoverers list, era-coloured periodic table and the name-origins explorer - [Element name origins](https://www.periodictable.one/history/name-origins): visual periodic table coloured by name source (place, properties, person, mythology, astronomical, mineral) with the language of origin marked in each cell. Includes 17 filter sub-pages (six source types, eleven languages) and a sortable table view at `?view=table`. Each filter sub-page (e.g. `/history/name-origins/place` or `/history/name-origins/greek`) is its own indexable list of matching elements with an intro paragraph and FAQ. - [Properties overview](https://www.periodictable.one/properties): atomic weight, color, electron configurations, heat of vaporization, ionization energies - [About](https://www.periodictable.one/about): who runs the site (Injosoft AB, founded 2018-03-10), data sources, sister projects (arcynia.com, ascii-code.com, asciiart.eu) and contact details - [Search](https://www.periodictable.one/search): name and symbol lookup ## Games section (English) Four free browser games built around the periodic table. No signup, no ads, runs entirely client-side after a single page load. All games have local top-5 leaderboards (stored in `localStorage`) and a profanity filter on submitted names. - [Games overview](https://www.periodictable.one/games): card grid of every game in the catalogue, with `ItemList` JSON-LD describing each entry. - [Element Merge](https://www.periodictable.one/game/element-merge): 2048-style puzzle. Slide tiles to combine pairs of the same element; each merge advances one step up the periodic table. - [Element Drop](https://www.periodictable.one/game/element-drop): falling-block arcade. Sort each tumbling element into its family - alkali metal, noble gas, halogen or transition metal - before it hits the floor. - [Element Sorter](https://www.periodictable.one/game/element-sorter): reflex / drag-and-drop. Cards fall from above; drag each into the correct broad category (metals, nonmetals, noble gases, metalloids) before it scrolls off-screen. - [Noble Gas Escape](https://www.periodictable.one/game/noble-gas-escape): canvas-based Pac-Man clone. Play as Neon dodging reactive Fluorine, Chlorine and Potassium across four mazes, collecting electrons and grabbing a helium shield for short invulnerability windows. Each per-game page exposes `VideoGame` JSON-LD (genre, applicationCategory: GameApplication, operatingSystem: Web Browser, free offer, family-friendly flag) so AI assistants and rich-results crawlers can categorise the catalogue without scraping the UI. ## Quiz section (English) Six free interactive quiz modes, no signup required, translated into all 4 languages. Each quiz can be played as 10, 20, 50, or all 118 questions (no element repeats), plus 1-minute, 2-minute, or endless timed modes. - [Quiz overview](https://www.periodictable.one/quiz): six quiz modes - [Element symbol quiz](https://www.periodictable.one/quiz/symbol): memorise all 118 chemical symbols - [Atomic number quiz](https://www.periodictable.one/quiz/atomic-number): match elements to their atomic numbers - [Element category quiz](https://www.periodictable.one/quiz/category): identify metals, nonmetals, metalloids, noble gases, halogens, transition metals - [Find the element](https://www.periodictable.one/quiz/find-element): click the correct cell on a compact periodic table - [True or false](https://www.periodictable.one/quiz/true-false): decide whether statements about elements are true or false - [Mixed multiple choice](https://www.periodictable.one/quiz/multiple-choice): all question types in one quiz, four options per question Each quiz page also has a FAQ section covering pedagogical questions about the topic (why some symbols come from Latin, what atomic number measures, how the periodic table is organised, etc.). ## Language alternates The same pages are available in: - Swedish: `/sv/` (e.g. `/sv/grundamne/1`, `/sv/quiz/symbol`). This document in Swedish: [/sv/llms.txt](https://www.periodictable.one/sv/llms.txt) - Danish: `/da/` (e.g. `/da/grundstof/1`, `/da/quiz/symbol`). This document in Danish: [/da/llms.txt](https://www.periodictable.one/da/llms.txt) - Spanish: `/es/` (e.g. `/es/elemento/1`, `/es/cuestionario/simbolo`). This document in Spanish: [/es/llms.txt](https://www.periodictable.one/es/llms.txt) Use the `` tags in each page's `` to discover translated versions. ## Structured data Every page exposes `application/ld+json` with a `@graph` array containing: - `Organization` (Injosoft AB, publisher) - `WebSite` and `WebPage` (with `inLanguage`) - `BreadcrumbList` Additional types per page type: - **Element pages**: `ChemicalSubstance` with `name`, `alternateName` (symbol), `molecularFormula`, `iupacName`, `additionalProperty` array (atomic number, mass, period, block, group, melting/boiling point, density, CAS number, electron configuration, discovery year/person). Plus `Article` and `Person` for the discoverer. - **History timeline**: `Event` for each discovery milestone. - **Quiz overview**: `ItemList` of the six quiz modes. - **Quiz subpages**: `Quiz` with `learningResourceType`, `educationalLevel`, `isAccessibleForFree`, plus 6-10 curated `Question`/`Answer` pairs as `hasPart`. - **All quiz pages**: `FAQPage` with `mainEntity` containing 3-5 pedagogical `Question`/`Answer` pairs about the topic. - **Property pages**: `Dataset` and `ItemList` of the 118 elements ranked by the property. ## Crawling Standard `robots.txt` applies. `/wallda/`, `/docs/`, `/cache/`, `/backoffice/`, `/beta22/`, `/styles/`, `/llms/` are disallowed. No rate limit, but please cache aggressively, this is mostly static content (element data changes rarely; UI translations may change). The sitemap's `lastmod` reflects when the sitemap was generated, not when individual data changed. ## Maintainer [Injosoft AB](https://www.injosoft.se/)