Periodic Table Help

A guide to every part of the Elemental Periodic Table and where its values come from.

Last Updated: November 12, 2026

1. Getting Started

The tool has five tabs under the heading: Table, Trends, Compare, Lab and Quiz. Everything happens on this page; nothing is uploaded and there is no account. Your settings and best quiz scores are kept in this browser once you change one, and the page works the same on a phone, where the table fits the screen and the List view gives every element a full row.

2. Reading the Table

Each square is one element, with its atomic number top left and its symbol in the middle; on wider screens its name and a value are shown too. The coloured edge shows the family (alkali metals, alkaline earth metals, transition metals, post-transition metals, metalloids, reactive nonmetals, noble gases, lanthanides, actinides, and elements whose chemistry is unknown). The fill shows the state at the temperature on the slider: full for a solid, half for a liquid, empty with a dashed edge for a gas.

On a computer, pointing at a square shows its details in the space above the transition metals. Choose a square, or press Enter on it, to open its window. The lanthanides and actinides sit in the two rows below; the squares marked 57-71 and 89-103 pick them out. The numbers along the top and side pick out a group or a period.

3. Search and Filters

The search box picks out matching elements and dims the rest. It accepts names (also aluminum, sulphur, cesium and wolfram), symbols, atomic numbers, families, "group 14", "period 4", "d-block", "solid", "liquid" or "gas" at the current temperature, "radioactive", "synthetic", "metals", "nonmetals" and "rare earths". Enter opens the element when there is one match. The buttons in the legend pick out a family, a state or the radioactive elements; choose one again to clear it.

4. Temperature and States

Drag the temperature slider from absolute zero (0 K) to 6000 K, or choose a preset: absolute zero, liquid nitrogen (77 K), room (25 °C), boiling water, lava (1200 °C) and the Sun's surface (5772 K). The value shows in °C, K or °F; a glowing dot shows the colour hot matter glows at that temperature. The state buttons in the legend count how many elements are solid, liquid, gas or unknown at that temperature.

• Helium never freezes at normal pressure, so it is liquid below 4.2 K.
• Carbon and arsenic turn straight from solid to gas (sublime) at normal pressure, at about 3825 °C and 616 °C.
• Unknown: where a melting point has never been measured, or an element has melted and its boiling point is unknown (francium, radium and several actinides), the square is hatched.

5. History of Discovery

The Known by slider fades out the elements not yet discovered in the chosen year, from 1640 to today, and names the year's discoveries or a moment in the history of the table (Hennig Brand's phosphorus in 1669, Lavoisier's list in 1789, Mendeleev's table in 1869, five elements in 1898, the first artificial element in 1937). Replay history runs through the years in about 16 seconds; move the slider to stop it. The Trends tab's Discovery chart shows the same history as a staircase, with the elements of each era listed below it.

6. Colour by a Property and the List

Colour by switches the squares from families to the block (s, p, d, f), where each element comes from (primordial, from decay, synthetic) or a property: atomic weight, electronegativity, ionisation energy, electron affinity, atomic radius, covalent radius, density, melting point, boiling point, abundance in the crust or year of discovery. Darker means more; hatched squares have no value. The scale under the table shows the lowest and highest values and marks the element you point at. Abundance uses powers of ten.

List shows every element as a row, sortable by any column, and follows the search and filters.

7. An Element's Window

An element's window shows its facts (atomic number, atomic weight, position, state at the chosen temperature, melting and boiling points, density, electronegativity, ionisation energy, electron affinity, radii, oxidation states, abundance and where it comes from), each with a small strip showing where it ranks among all elements. Below are its electrons (configuration, a shell diagram and the outer orbitals as boxes), where it sits in the table, its story (when and by whom it was found and where its name comes from) and its uses.

Add to Compare puts it in the Compare tab, Copy link copies a link to it, and Read on Wikipedia opens its Wikipedia article in a new tab (only when you choose it). The arrows at the top, or the left and right arrow keys, step to the previous and next element.

8. Trends

Across the table charts one property against atomic number, with the periods shaded and a family marked (noble gases, alkali metals, halogens, the carbon group, copper, silver and gold, or the lanthanides): the repeating pattern is why the table is periodic. Two properties plots one against another for every element that has both, with the correlation and a best-fit line when the link is clear. Discovery shows the number of known elements over time. Point at the chart or use the left and right arrow keys to read each value; Show the numbers lists them all.

9. Compare

Type an element into the box or pick a ready-made set (alkali metals, halogens, noble gases, copper, silver and gold, carbon and silicon, lightest and heaviest) to put up to four elements side by side. Each property shows its value and a bar from the lowest to the highest among all elements, and the highest of the group is marked. Copy a link to this comparison copies a link that opens the same comparison.

10. Molar Mass and Empirical Formulas

Type a formula: symbols start with a capital (Co is cobalt, CO is carbon monoxide), brackets of any kind group atoms, and a dot or a centred dot adds water of crystallisation (CuSO4.5H2O). Subscript digits pasted from elsewhere are read too. The result is the molar mass in g/mol, the number of atoms in one formula unit, the formula in Hill order and a table with each element's share of the mass; below it, grams, moles and the number of formula units convert into each other (with the Avogadro constant, 6.02214076 × 10²³ per mole). For radioactive elements the mass number of the longest-lived isotope is used, and the result says so.

For an empirical formula, enter each element's symbol and mass percentage from an analysis. The tool works out moles in 100 g, divides by the smallest and multiplies until every number is close to a whole one (up to 12 times). With a molar mass, it also gives the molecular formula. Counts of zero, percentages above 100 and an element listed twice are refused with a message.

11. Balancing Equations

Type the reactants and products with + between substances and = or -> (or an arrow) between the sides. A number in front of a substance is ignored, states such as (aq) or (s) are allowed, ions are written with ^ (Fe^3+, MnO4^-, SO4^2-) and an electron as e^-. The balancer finds the smallest positive whole numbers with exact fractions, so even large coefficients are right, and checks every element and the charge in a table. It handles up to 20 substances and 200 characters.

12. Molecules in 3D

Pick a molecule below the model. Drag to turn it, scroll or pinch to zoom, or use the arrow keys and + and - when the model has focus. Ball and stick shows bonds (double and triple bonds as two and three lines) and lone pairs as faint clouds; Space filling shows the atoms at their van der Waals size. Labels writes each atom's symbol, Spin turns the model slowly (off when your device asks for reduced motion), and Reset returns to the first view. The panel beside it gives the shape, the bond angle and whether the molecule is polar.

13. The Quiz

Find it, Name it, Symbol and Family are rounds of ten questions over the first 20, 54 or all 118 elements; answer by choosing, or press 1 to 4. Each answer says whether it was right and gives a fact about the element. At the end you see your score, your best for that round and the elements worth another look. All 118 asks you to type every element's name from memory; each one you get lands in its place, the clock runs from the first letter, and Give up shows the ones you missed.

14. Where the Values Come From

• Standard atomic weights: CIAAW, Standard Atomic Weights 2024, abridged to five figures as CIAAW publishes them. In square brackets: the mass number of the most stable isotope from CIAAW's list of the radioactive elements, based on NUBASE2020.
• Melting and boiling points, densities, Pauling electronegativity, electron affinity, crust abundance: the CRC Handbook of Chemistry and Physics (95th and 97th editions), taken from the open mendeleev data set, which records the source of each property. Densities of gases are those of an ideal gas at 25 °C and normal pressure. Estimates the data set marks as such are not shown; nor are calculated electron affinities for polonium, francium, radium, actinium and oganesson. Astatine's electron affinity is the value measured in 2020 (Leimbach and others).
• First ionisation energies: the NIST Atomic Spectra Database; for elements 104 and above only calculations exist, so none is shown.
• Covalent radii: Cordero and others (2008), carbon as in a single bond and manganese, iron and cobalt in their low-spin form. Atomic radii: Rahm, Hoffmann and Ashcroft (2016 and 2017), calculated for the free atom.
• Discovery: the year an element was recognised or isolated, following PubChem's periodic table or Wikidata wherever either agrees; fluorine as in its Nobel Prize citation; elements 102, 105 and 107 as credited by the IUPAC and IUPAP Transfermium Working Group (1993).

15. How It Was Checked

Before publishing, every value was compared with its source, and the tool's calculations with a separate program written from the rules on this page: 738,787 cases in 13 groups, among them every element's values against CIAAW and the CRC and NIST data, the states of every element at thousands of temperatures, molar masses of thousands of formulas with brackets, hydrates and charges against an independent calculation, empirical formulas worked back from percentages, and hundreds of equations balanced against exact linear algebra, including ones that cannot balance. The page was then tested in a browser on phones and computers in both themes, with long and hostile input, blocked storage and the keyboard. The original version used older atomic weights for argon and zirconium, mixed values from different sources, showed a count of zero as "NaN%", stopped on a link with a stray % sign and took saved data without checking it; that is fixed.

16. Privacy, Keyboard and Troubleshooting

• Privacy. Nothing you type is uploaded. Settings and best scores stay in this browser on this device, under this tool's own name; a private window or cleared site data starts afresh.
• Keyboard. Arrow keys move between tabs and around the table, Enter opens an element, / jumps to the search while you use the tool, 1 to 4 answer the quiz, and Escape closes a window.
• A symbol is not recognised. Check the capitals: the first letter is a capital and the second a small letter.
• An element shows unknown. No measured value exists in the sources; see section 14.
• Copy link does nothing. The browser blocked the clipboard; the message shows the link to copy by hand.

For questions the FAQ does not answer, use the contact form.