Interactive Periodic Table of the Elements
Tap any element to see all its data. Search by name, symbol or atomic number, or use the filters to show only halogens, the d-block or every gas, for example.
How it is calculated
How the periodic table is organised
The periodic table arranges all 118 known chemical elements by atomic number Z – the number of protons in the nucleus. The 7 rows (periods) correspond to electron shells, and the 18 columns (groups) collect elements with the same number of outer electrons. That is why elements in a group behave alike: sodium and potassium both react violently with water, while helium and neon form almost no compounds.
How to use the periodic table
- Search for an element by name, symbol or atomic number, or click it in the table.
- Filter by category, block or state of matter – e.g. only halogens or all gases – or show the elements as a list.
- Read atomic mass, electron configuration, melting and boiling point in the details; the arrow keys move to the next element.
The blocks show which orbital is filled last: s-block (groups 1–2 plus helium), p-block (groups 13–18), d-block (transition metals, groups 3–12) and f-block (lanthanides and actinides, shown separately below). Here lutetium and lawrencium sit in group 3 – a layout IUPAC is still reviewing in an ongoing project.
Reading an element – chlorine as an example
- Atomic number 17: 17 protons, and 17 electrons in the neutral atom.
- Period 3: the electrons occupy 3 shells: [Ne] 3s² 3p⁵.
- Group 17 (halogens): 17 − 10 = 7 outer electrons; it is one short of a noble-gas configuration, so chlorine forms Cl⁻ ions.
- Atomic mass 35.45: the weighted average of the isotopes ³⁵Cl and ³⁷Cl. One mole of chlorine atoms weighs 35.45 g. Neutrons in the most common isotope: 35 − 17 = 18.
Where the data comes from
Atomic masses are the abridged standard atomic weights of the IUPAC Commission CIAAW (2021 values, including the 2024 revisions for gadolinium, lutetium and zirconium). Elements with no stable isotopes – technetium, promethium and everything from polonium upwards except thorium, protactinium and uranium – have no standard atomic weight; their tile shows the mass number of a long-lived isotope in square brackets, e.g. [97] for technetium. All other values – electron configuration, electronegativity, melting and boiling points, density, year of discovery – come from the public-domain PubChem Periodic Table of the US National Library of Medicine; element names in other languages come from Wikidata. For the superheavy elements, state and configuration are only predicted.
Use the atomic masses to work out the molar mass of a compound: M(H₂O) = 2 × 1.0080 + 15.999 = 18.015 g/mol.
Calculate with the data: compounds with the molar mass calculator, mass and volume with the density calculator, and radioactive decay with the half-life calculator.
Frequently asked questions
How many elements are in the periodic table?
118 at present. The four newest – nihonium (113), moscovium (115), tennessine (117) and oganesson (118) – were named by IUPAC in 2016, which completed period 7.
What does the number in square brackets mean?
The element has no stable isotopes and therefore no standard atomic weight. The bracketed number is the mass number of a long-lived isotope as listed by PubChem, e.g. [97] for technetium. The detail view shows the exact isotope mass.
What is the difference between atomic number and mass number?
The atomic number is the number of protons and defines the element. The mass number is the total of protons and neutrons in one particular isotope. Carbon always has atomic number 6; its most common isotope, carbon-12, has mass number 12 (6 protons + 6 neutrons).
Which elements are liquid at room temperature?
Under standard conditions only mercury and bromine. Gallium (melting point 29.76 °C) and caesium (28.44 °C) melt just above – gallium will even melt in your hand. Try the “State of matter” filter.
Why are the lanthanides and actinides shown at the bottom?
Purely to save space: with the 14 f-block elements in each period the table would be 32 columns wide. They belong between groups 2 and 3 in periods 6 and 7.
How do I find an element quickly?
Type its symbol, name or atomic number into the search box. When only one element matches, pressing Enter opens its details straight away.
Sources and legal basis
- PubChem Periodic Table (NCBI/NLM) – element data, public domain, retrieved 27 Sep 2026
- IUPAC CIAAW – Abridged Standard Atomic Weights (Atomic Weights 2021, Revision 2024)
- IUPAC – Periodic Table of Elements (4 May 2022 release, note on group 3)
- Wikidata – element names (labels, CC0)
As of:
Related tools
- Molar Mass CalculatorCalculate molar mass in g/mol from any chemical formula – with brackets, hydrates like CuSO4·5H2O, mass percent by element, working steps and n = m/M.
- pH calculator with step-by-step solutionCalculate the pH of strong and weak acids and bases – exact quadratic solution, pKa/pKb or Ka/Kb, and conversion between pH, pOH, [H₃O⁺] and [OH⁻].
- Density calculator: density, mass and volumeCalculate density, mass or volume with ρ = m/V – step-by-step, with unit conversion from g/cm³ to kg/m³ and lb/ft³ and densities of water, metals and plastics.
- Half-life calculatorSolve for half-life, remaining amount, initial amount or time – with decay constant λ, mean lifetime, percent left and full working. C-14, I-131 and more.
- Scientific Notation Converter with StepsConvert numbers to and from scientific notation: a × 10ⁿ, E notation, engineering notation with SI prefixes and standard form – exact, step by step.
- Significant Figures CalculatorCount significant figures, round to n sig figs and apply the rules for multiplying and adding – with highlighted digits, full working and scientific notation.