Interactive Periodic Table
Every element’s data, trend heat maps, search, filters and side-by-side comparison.
Periodic table
On a small screen, scroll the table sideways. Arrow keys move between elements; Enter or Space shows its details. The value under each symbol follows “Colour by”.
Elements
Hydrogen
Isotopes
Side by side
About the Interactive Periodic Table
A periodic table you can explore. Every one of the 118 elements carries its standard atomic weight from the IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW 2024, including the 2024 revisions for gadolinium, lutetium and zirconium), its ground-state electron configuration and first ionization energy from the NIST Atomic Spectra Database, and its electronegativity, van der Waals and covalent radii, electron affinity, density, melting and boiling points, oxidation states and year of discovery from PubChem. Each element also lists its natural isotopes and their abundances, or — for radioactive elements with no standard atomic weight — its longest-lived known isotope and half-life.
Colour the table by category, block or state, or turn it into a heat map of any property to see the periodic trends. Search by name, symbol or atomic number (US and Latin names work too), highlight a block, group, period or category, switch to a sortable list on a phone, and add up to four elements to a side-by-side comparison. Everything can be copied or downloaded as CSV.
How to use it
- Type a name, symbol or atomic number in Search, or click any element (arrow keys move between elements; Enter opens one).
- Read the element’s details below the table: atomic weight, configuration, energies, radii, temperatures, isotopes and notes.
- Choose Colour by to switch between categories, blocks, states and heat maps such as electronegativity or ionization energy; the legend explains the colours.
- Use Highlight to pick out a block, group, period or category. List shows the same elements as a table you can sort by any column.
- Press Compare on up to four elements to see them side by side, and Download CSV for the full data set.
Examples
Search “Fe” or “26”
Standard atomic weight 55.845(2); [Ar] 3d⁶ 4s²; first ionization energy 7.902 eV; electronegativity 1.83; isotopes ⁵⁴Fe, ⁵⁶Fe (91.754 %), ⁵⁷Fe, ⁵⁸Fe
Carbon
[12.0096, 12.0116] — abridged to 12.011 ± 0.002, because carbon’s isotopic mix varies in nature
Technetium
No standard atomic weight; most stable isotopes ⁹⁷Tc (4.21 million years) and ⁹⁸Tc (4.2 million years)
Colour by electronegativity
Fluorine is highest (3.98) and caesium and francium lowest (0.79 and 0.7): it rises across a period and falls down a group
Colour by first ionization energy
Caesium needs only 3.894 eV; helium needs 24.587 eV
Common uses
- Chemistry homework and revision: atomic weights for molar masses, configurations, and trends across periods and groups.
- Checking the current IUPAC (CIAAW) atomic weight of an element and how precisely it is known.
- Looking up natural isotope abundances or the longest-lived isotope of a radioactive element.
- Comparing related elements, such as the alkali metals or the halogens, property by property.
- Teaching periodic trends with heat maps of radius, electronegativity or ionization energy.
What the properties mean
- Standard atomic weight — the average mass of an element’s atoms in normal materials, relative to 1/12 of carbon-12. Fourteen elements, such as hydrogen and carbon, are given as an interval [a, b] because their isotopic mix varies naturally; the abridged value is for everyday calculations. Radioactive elements without one show the mass number of their longest-lived isotope in brackets, as in [97].
- Electron configuration — how the electrons fill the orbitals in the lowest-energy (ground) state, with the noble-gas core in brackets; the ground level (term symbol) is NIST’s.
- Electronegativity (Pauling scale) — how strongly an atom attracts the electrons in a bond.
- Van der Waals radius — half the distance of closest approach of non-bonded atoms; covalent radius — half the distance between two identical atoms joined by a covalent bond.
- First ionization energy — the energy to remove the most loosely bound electron from a gaseous atom; electron affinity — the energy released when a gaseous atom gains an electron.
- Density (gases at 0 °C and 1 atm), melting and boiling points in kelvins with °C and °F, oxidation states and the year of discovery.
Periodic trends
Within a period, atoms get smaller from left to right as the effective nuclear charge rises; down a group they get larger as electrons occupy higher shells. Electronegativity rises across a period and falls down a group, so fluorine is the most electronegative element and the group 1 metals the least (OpenStax Chemistry 2e §6.5 and §7.2). First ionization energies follow electronegativity in broad terms: highest for the noble gases and lowest for the alkali metals. The heat maps let you check each trend — and spot the exceptions, such as the dips in ionization energy from beryllium to boron and from nitrogen to oxygen.
About the layout
The table follows the conventional long form of the IUPAC Periodic Table of the Elements: group 3 shows scandium and yttrium above the lanthanoid (57–71) and actinoid (89–103) series, which sit in two rows below the main table so it fits a page. Which elements belong in group 3 — lanthanum and actinium, or lutetium and lawrencium — is still debated, and IUPAC has a project on it. IUPAC prefers the names lanthanoid and actinoid to lanthanide and actinide. The categories (alkali metal, metalloid and so on) are those used by PubChem; “reactive nonmetal” covers hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur and selenium, with the halogens and noble gases shown separately.
Sources
- IUPAC CIAAW, Standard Atomic Weights 2024, Abridged Standard Atomic Weights 2024, Isotopic Compositions of the Elements 2024 and Radioactive Elements (from NUBASE2020, Kondev et al., Chinese Physics C 45, 030001).
- NIST, Atomic Spectra Database — ionization energies (ground shells, ground levels and first ionization energies; semi-empirical and theoretical values are marked).
- PubChem Periodic Table and element records (NCBI, public domain; data from Jefferson Lab, Los Alamos National Laboratory and PubChem Elements).
- IUPAC, Periodic Table of the Elements.
- OpenStax, Chemistry 2e (CC BY 4.0): §6.5 Periodic Variations in Element Properties and §7.2 Covalent Bonding.
Limitations
- Properties of the superheavy elements (Z ≥ 104) are mostly predictions, and some have no data at all.
- Densities, melting and boiling points refer to one allotrope or form (graphite for carbon, for example) at normal pressure; other forms differ.
- Radii depend on how they are defined and measured; compare like with like.
- Oxidation states list the common ones reported by PubChem, not every state known in unusual compounds.
- Category boundaries such as metalloid and post-transition metal are conventions, not IUPAC definitions.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
How many elements are there?
118, from hydrogen (1) to oganesson (118). All of them up to oganesson have been made or found and named; oganesson was first reported in 2006 (PubChem).
Why are some atomic weights given as a range?
Because the mix of isotopes of those elements varies in nature. CIAAW gives hydrogen, lithium, boron, carbon, nitrogen, oxygen, magnesium, silicon, sulfur, chlorine, argon, bromine, thallium and lead as intervals — carbon is [12.0096, 12.0116] — and an abridged value such as 12.011 ± 0.002 for everyday use.
What is the atomic weight of an element without stable isotopes?
It has no standard atomic weight. Tables show the mass number of its longest-lived isotope in square brackets instead — for example [97] for technetium and [294] for oganesson.
Which element is the most electronegative?
Fluorine, with 3.98 on the Pauling scale. Electronegativity rises across a period and falls down a group, so the lowest values are at the bottom left: caesium 0.79 and francium 0.7.
Which element has the highest first ionization energy?
Helium: 24.587 eV to remove one electron (NIST). Caesium has the lowest, 3.894 eV.
Why are the lanthanides and actinides shown below the table?
To keep the table a practical width. They belong in periods 6 and 7 between groups 2 and 4; printing them in place gives a 32-column table. IUPAC calls them lanthanoids and actinoids.
What is the difference between atomic number and mass number?
The atomic number is the number of protons and defines the element (iron is always 26). The mass number is protons plus neutrons and differs between isotopes: iron-54, iron-56, iron-57 and iron-58.