Interactive Periodic Table

Selected element

Legend: Category

• AMAlkali metal · 6 elements
• AEAlkaline earth metal · 6 elements
• TMTransition metal · 38 elements
• PTPost-transition metal · 11 elements
• MDMetalloid · 7 elements
• NMNonmetal · 7 elements
• HLHalogen · 6 elements
• NGNoble gas · 7 elements
• LNLanthanide · 15 elements
• ACActinide · 15 elements

How to Use the Periodic Table

1. 1. Pick an element. Click a tile, or press Tab once to enter the table and use the arrow keys to move around it. Enter or Space selects the element, and its details appear above the table.
2. 2. Search if you know what you want. Type a name (gold), a symbol (Au), an atomic number (79) or a category (halogen). Matching tiles get a heavy outline and the others fade, so the matches stay visible in the table's layout.
3. 3. Change the colouring. Choose category, block, electronegativity or year of discovery. The legend under the controls gives each colour a short code that is also printed on every tile, so you never need the colour alone.
4. 4. Switch to the list for exact numbers. The list view shows every element in a table with weight, group, period, block, category, electronegativity and discovery year, and it follows your search.

What Each Property Means

Reading Electronegativity

Linus Pauling's scale is dimensionless and anchored at fluorine, 3.98, the most electronegative element. Values fall as you move down a group and rise as you move across a period, so the extremes sit in opposite corners of the table: fluorine at the top right, caesium and francium at the bottom left. The noble gases helium, neon, argon and radon have no accepted Pauling value, and neither do promethium, europium, terbium, ytterbium or any element from rutherfordium upward. Several of the actinide values are estimates.

Subtracting two values gives a rough guide to a bond. Many textbooks treat a difference below about 0.4 as nonpolar covalent, 0.4 to about 1.7 as polar covalent, and above that as ionic — but the cut-offs differ between books, and an element's value shifts with its oxidation state, so treat them as a first estimate. Sodium (0.93) and fluorine (3.98) differ by 3.05, which is why sodium fluoride is ionic; two carbon atoms differ by 0, so the C–C bond is nonpolar.

Electron Configurations and Their Exceptions

Most configurations follow the Madelung order: fill 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p. The tool writes subshells in order of shell number, as NIST does, so iron reads [Ar] 3d⁶ 4s² rather than [Ar] 4s² 3d⁶. About twenty elements break the pattern in measured ground states, because the 3d and 4s (or 4d and 5s, 4f and 5d, 5f and 6d) subshells are close in energy and a half-filled or filled d subshell can be slightly lower overall.

Worked Example: Iron

Select Fe and the table gives atomic number 26, atomic weight 55.845, group 8, period 4, d-block, Pauling electronegativity 1.83, a transition metal known since antiquity, with configuration [Ar] 3d⁶ 4s². Reading it back: period 4 because the highest occupied shell is n = 4; d-block because the last electrons go into 3d; group 8 because for a d-block element the electrons outside the noble-gas core (six in 3d plus two in 4s) add up to the group number.

Group 3, the F-Block and Hydrogen

• Group 3 holds Sc, Y, Lu and Lr, following IUPAC's 2021 provisional recommendation. That leaves La–Yb and Ac–No as two rows of 14, drawn below the table so it stays 18 columns wide. Older tables put La and Ac in group 3 instead.
• Hydrogen sits in group 1 because of its 1s¹ configuration, even though it is a nonmetal in category. Some tables place it over fluorine or in the middle.
• Categories follow the PubChem scheme (alkali metal, alkaline earth metal, transition metal, post-transition metal, metalloid, nonmetal, halogen, noble gas, lanthanide, actinide). Textbooks draw the metalloid line and the heaviest elements' labels differently, so a category is a convention, not a measurement.
• Discovery years are conventions too: for some elements the date is first recognition, for others first isolation. Fluorine is dated to Moissan's 1886 isolation, not to the earlier use of fluorspar.

Where the Data Come From

Atomic weights are the IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW) abridged standard values for 2024, the same ones used by the Molar Mass Calculator. Electronegativity, category and discovery year come from the PubChem Periodic Table, whose Pauling values follow the CRC Handbook of Chemistry and Physics. Electron configurations are the Madelung filling with the measured exceptions listed in the NIST Atomic Spectra Database. The page runs entirely in your browser — nothing is uploaded.

Frequently Asked Questions

How many elements are there in the periodic table?

There are 118 named elements, filling seven periods. Hydrogen to plutonium (1–94) are generally counted as occurring on Earth, though technetium, promethium, neptunium and plutonium only in trace amounts; americium (95) and everything heavier have only been made in laboratories. IUPAC recognised elements 113, 115, 117 and 118 in December 2015 and approved their names in 2016.

Which element has the highest electronegativity?

Fluorine, at 3.98 on the Pauling scale; oxygen is next at 3.44, then chlorine at 3.16 and nitrogen at 3.04. The lowest value in the table is francium's estimated 0.7, and caesium, at 0.79, is the lowest measured value.

Why are the lanthanides and actinides shown separately?

Writing them in sequence would make periods 6 and 7 each 32 columns wide, so the 14 f-block elements are drawn in two rows below the main table. In this table Lu and Lr stay in group 3, which is IUPAC's 2021 provisional recommendation; older tables put La and Ac there instead.

What do the brackets around an atomic weight mean?

A bracketed number is not a standard atomic weight. Elements such as technetium [98] and plutonium [244] have no stable isotopes in a composition that would define one, so tables give the mass number of the longest-lived known isotope. Use it as an approximation, as the Molar Mass Calculator does.

Why does chromium have the configuration [Ar] 3d⁵ 4s¹?

The 3d and 4s subshells are very close in energy in this region, and moving one electron from 4s to 3d gives a half-filled d subshell with a slightly lower total energy. The Madelung order would predict 3d⁴ 4s², but spectroscopy shows 3d⁵ 4s¹. Copper (3d¹⁰ 4s¹) is the filled-subshell version of the same effect.

What is the difference between a group and a period?

A group is a vertical column, numbered 1–18, and its elements share a valence-electron pattern, so they react in similar ways: the alkali metals of group 1, the halogens of group 17. A period is a horizontal row, numbered 1–7, and corresponds to the shell that is being filled.

Is hydrogen a metal or a nonmetal?

Under normal conditions hydrogen is a nonmetal, a diatomic gas, although it is placed in group 1 because its configuration, 1s¹, has one valence electron like the alkali metals. This table colours it as a nonmetal and puts it in group 1; some tables place it above fluorine or alone.