Interactive Periodic Table
All 118 elements with live heatmaps, a temperature slider, a discovery timeline, electron configurations, orbital and Bohr diagrams, isotopes, side-by-side comparison, a formula builder and a quiz. Data from PubChem (NIH), NIST and IUPAC.
How to Use
- Click any element (or move to it with the arrow keys and press Enter) to open its details: properties with units, the electron configuration, an orbital box diagram, a Bohr shell model, isotopes, and notes on its name and discovery.
- Use Colour by to switch from categories to blocks, states, or a heatmap of a property such as electronegativity, ionization energy, atomic radius, melting point or density. Toggle linear or log scale for the wide-ranging ones.
- Drag the temperature slider to see which elements are solid, liquid or gas at 1 atm. At 298.15 K (25 °C) only bromine and mercury are liquid. Drag the discovery slider back to 1869 to see the 63 elements Mendeleev had to work with.
- Search by name, symbol, number or category, or set a property range (for example melting point 300 to 600 K) to dim everything else. The trend chart under the table plots the property against atomic number, period by period.
- Switch the mode to Compare (pick 2–3 elements), Build formula (click H, H, O to get H₂O at 18.015 g/mol) or Quiz. Every view has its own URL, so Copy link shares exactly what you see.
All 118 elements shown
Iron, element 26. Details load with the page script.
Worked Example
Reading iron (Fe) off the table. Iron is element 26, so a neutral atom has 26 electrons. Filling subshells in the Madelung order gives 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶ (2 + 2 + 6 + 2 + 6 + 2 + 6 = 26), written [Ar] 3d⁶ 4s². The argon core closes period 3, so iron is in period 4; its 4s² + 3d⁶ = 8 outer electrons put it in group 8. The shells hold 2, 8, 14 and 2 electrons, and Hund’s rule leaves 4 of the six 3d electrons unpaired, which matches NIST’s ground term ⁵D₄ (2S + 1 = 5). The standard atomic weight is 55.845, the electronegativity 1.83, and the first ionization energy 7.9024681 eV, which is 7.9024681 × 96.485 = 762.47 kJ/mol.
Is iron liquid at 2000 K? Iron melts at 1811 K (1537.85 °C) and boils at 3134 K (2860.85 °C). Since 1811 ≤ 2000 < 3134, it is liquid at 2000 K and 1 atm. Chlorine, by contrast, boils at 239.11 K (−34.04 °C), so at 298.15 K it is a gas. Its configuration [Ne] 3s² 3p⁵ gives 2 + 5 = 7 valence electrons and group 10 + 7 = 17; gaining one electron makes Cl⁻, [Ne] 3s² 3p⁶, the same as argon.
The common mistake: taking ion electrons from the last subshell filled. The 3d subshell fills after 4s, so it is tempting to write Fe²⁺ as [Ar] 3d⁴ 4s². The right answer is [Ar] 3d⁶: once 3d is occupied, the 4s electrons are the outermost and leave first, and Fe³⁺ is [Ar] 3d⁵. The same trap applies to neutral chromium, where the filling rule gives [Ar] 4s² 3d⁴ with 4 unpaired electrons, but the real atom is [Ar] 3d⁵ 4s¹ with 6.
Show Work
Formulas
From Mendeleev to Oganesson
Dmitri Mendeleev published his periodic table in 1869, when 63 elements were known. He ordered them by atomic weight, grouped them by their chemistry, and left gaps for elements nobody had found yet, predicting the properties of “eka-aluminium”, “eka-boron” and “eka-silicon”. They turned up as gallium (1875), scandium (1879) and germanium (1886). Lothar Meyer reached a very similar arrangement independently, and his plot of atomic volume against atomic weight showed the repeating pattern that gives the table its name.
Ordering by weight left a few pairs the wrong way round, such as argon (39.95) before potassium (39.098) and tellurium (127.60) before iodine (126.90). In 1913 Henry Moseley measured the X-ray frequencies of the elements and showed that they follow the nuclear charge, the atomic number Z, which is the order used today and the reason those pairs stay where Mendeleev put them. The noble gases had already been added as a new column after argon (1894) and neon, krypton and xenon (1898) were found.
In the mid-1940s Glenn Seaborg proposed that the elements from actinium onwards form a second f-block series, the actinides, which moved thorium, protactinium and uranium out of the d-block and gave the table its modern shape. The seventh period was completed when IUPAC approved the names nihonium, moscovium, tennessine and oganesson in November 2016, bringing the total to 118.
About This Tool
This periodic table is built for exploring, not just looking things up. Each of the 118 elements carries its IUPAC atomic weight, electron configuration, electronegativity, ionization energy, electron affinity, two kinds of atomic radius, melting and boiling points, density, oxidation states, crustal abundance, isotopes and discovery year. You can colour the table by any of them, watch states change with temperature, roll the discovery timeline back to antiquity, plot any property against atomic number, compare elements side by side, build formulas with their molar mass, and quiz yourself. The configurations, orbital diagrams, shell counts, ion configurations, groups and states are worked out live, and Show Work explains each step.
The data comes from PubChem’s periodic table and element records (U.S. National Library of Medicine, NIH), which collect NIST ionization energies and isotope compositions, IUPAC CIAAW atomic weights and IAEA nuclear data. Where PubChem’s own sources disagree, the table says so: helium only freezes under pressure, carbon and arsenic sublime at 1 atm, the discovery years of fluorine, aluminium, silicon and calcium follow the dates the element was isolated, and lawrencium’s last electron may be 7p rather than 6d. Values for the heaviest elements are estimates. It all runs in your browser and nothing is uploaded.
Related tools: Molar Mass Calculator, Chemical Equation Balancer, and Stoichiometry Calculator.
Frequently Asked Questions
Why are chromium and copper exceptions to the Aufbau principle?
Filling subshells in the Madelung (n + l) order predicts [Ar] 4s² 3d⁴ for chromium and [Ar] 4s² 3d⁹ for copper, but the measured ground states are [Ar] 3d⁵ 4s¹ and [Ar] 3d¹⁰ 4s¹. The 4s and 3d levels are so close that moving one electron into 3d, giving a half-filled or full d subshell, lowers the energy; chromium ends up with 6 unpaired electrons instead of 4. In PubChem’s configurations 19 elements break the simple rule (Cr, Cu, Nb, Mo, Ru, Rh, Pd, Ag, La, Ce, Gd, Pt, Au, Ac, Th, Pa, U, Np, Cm), and Show Work flags each one.
What is electronegativity?
How strongly an atom pulls the shared electrons of a bond towards itself. On Linus Pauling’s scale fluorine is the highest at 3.98 and caesium is 0.79 (francium is estimated at 0.7). It rises across a period, from sodium 0.93 to chlorine 3.16 in period 3, and falls down a group. The gap between two atoms hints at the bond type: in sodium chloride it is 3.16 − 0.93 = 2.23, a strongly ionic bond. Noble gases helium, neon and argon have no Pauling value.
How many elements are there, and when were the last ones named?
There are 118 known elements, which fill all seven periods. The four newest, nihonium (Nh, 113), moscovium (Mc, 115), tennessine (Ts, 117) and oganesson (Og, 118), were first reported between 2003 and 2010 and received their names from IUPAC on 28 November 2016. Everything from fermium (Z = 100) up has only ever been made a few atoms at a time, so their densities, melting points and even their states are predictions.
How does the temperature slider decide solid, liquid or gas?
It compares the temperature with each element’s melting and boiling points at 1 atm: below the melting point it is solid, between the two it is liquid, and at or above the boiling point it is gas. At 298.15 K (25 °C) that gives 2 liquids (bromine and mercury) and 11 gases; at 302.91 K (29.76 °C) gallium melts, and caesium has already melted at 301.59 K (28.44 °C). Helium never freezes at 1 atm, carbon and arsenic sublime straight to gas, and the 15 elements from rutherfordium on have no data, so they are shown as unknown.
Where does the data come from?
From PubChem, the U.S. National Library of Medicine’s chemistry database: its periodic table and its element records, which bring together NIST ionization energies and isotope masses and abundances, IUPAC (CIAAW) atomic weights, IAEA half-lives, and notes from Jefferson Lab and Los Alamos. The atomic weights shown are the IUPAC values the Molar Mass tool uses, so the two always agree. Everything runs in your browser and nothing is uploaded.
How do I use the Interactive Periodic Table?
Just type your numbers. The answer shows up right away — there is no button to press. Change anything and it updates by itself.
Is it free? Does it work without internet?
Yes to both. It is free with no sign-up, and once the page has loaded it keeps working even with no internet.
Where does my data go?
Nowhere — every calculation runs on your own device. Nothing you enter is uploaded, logged, or stored.
Common Use Cases
Electron configurations
Read off that iron is [Ar] 3d⁶ 4s² with 4 unpaired electrons, and that Fe³⁺ is [Ar] 3d⁵ because the 4s electrons leave first.
Revising periodic trends
Watch first ionization energy climb across period 3, from 5.14 eV for sodium to 15.76 eV for argon, then crash at potassium.
Molar masses from the table
Click H, H, O to build water and get 2 × 1.008 + 15.999 = 18.015 g/mol, then open it in the Molar Mass tool.
History of chemistry
Slide the discovery timeline to 1869 and see the 63 elements Mendeleev knew, with gaps where gallium (1875), scandium (1879) and germanium (1886) would go.
Materials questions
Find the densest element (osmium, 22.57 g/cm³) and the highest-melting metal (tungsten, 3695 K) with the heatmaps.
Classroom quiz
Run a find-the-element quiz on the first 36 elements or all 118 and try to beat your best streak.
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