Interactive Periodic Table of Elements

Tap an element to see its atomic mass, electron configuration, electronegativity and oxidation states. Use the buttons above to change the colors of the table; use the search box to find an element by symbol, name or atomic number.
57–71
89–103
Lanthanides
Actinides
Alkali metalsAlkaline earth metalsTransition metalsPost-transition metalsMetalloidsNonmetalsHalogensNoble gasesLanthanidesActinides

Data: IUPAC standard atomic weights; electronegativity on the Pauling scale. For the heaviest elements some values have never been measured, and the card says so.

Click any element to see its atomic mass, electron configuration, electronegativity and common oxidation states. Use the buttons to color the table by category, electronegativity, state at 77 °F (25 °C) or metals and nonmetals, and search by symbol, name or atomic number. Both American and British spellings work: type aluminum or aluminium.

How to read the periodic table

The periodic table arranges all 118 known elements by atomic number, which is the number of protons in an atom’s nucleus. Hydrogen is 1, carbon is 6, iron is 26 and oganesson is 118. Reading left to right along a row, the atomic number goes up by one each step.

Rows are called periods and there are seven of them. Columns are called groups and there are 18. Elements in the same group tend to behave alike, because they have the same number of electrons in their outer shell. That is why lithium, sodium and potassium (group 1) all react with water, and why helium, neon and argon (group 18) hardly react at all.

The colors show categories: alkali metals, alkaline earth metals, transition metals, post-transition metals, metalloids, nonmetals, halogens, noble gases, lanthanides and actinides. Textbooks do not all draw these lines in the same place, so the categories here follow one common scheme, and a few elements, such as hydrogen, are placed differently from book to book.

The two rows set apart below the main table are the lanthanides (elements 57 to 71) and the actinides (89 to 103). They belong in the table’s body, but showing them there would make it too wide to read, so they are usually drawn underneath.

The atomic mass on each card is in atomic mass units (amu, written u). For elements with no stable isotope, tables often give the mass number of the longest-lived isotope in brackets instead of an average.

Electronegativity

Electronegativity measures how strongly an atom pulls on the electrons it shares in a chemical bond. The card shows the Pauling scale, the most widely used one. Fluorine is the highest at 3.98, followed by oxygen (3.44), chlorine (3.16) and carbon (2.55). Hydrogen is 2.20 and sodium is 0.93. Values generally rise from left to right across a period and fall going down a group.

Switch the color mode to electronegativity and the pattern shows up at once: the strongest pullers cluster at the top right, the weakest at the bottom left. Helium, neon and argon have no Pauling value because they form almost no bonds.

A rule of thumb is to subtract the two values. A difference above about 1.7 usually means an ionic bond, between about 0.4 and 1.7 a polar covalent bond, and below about 0.4 a nonpolar one. In table salt, chlorine (3.16) minus sodium (0.93) is 2.23, so sodium chloride is ionic. These cut-offs are conventions, not sharp boundaries.

Oxidation states

An oxidation state is the charge an atom would have if every bond in the compound were fully ionic. It is a bookkeeping tool: it helps you balance reactions and see which atom gives up or gains electrons. The card lists the common ones, not every state an element can reach.

Some follow simple patterns. Sodium is +1 in its compounds, and oxygen is almost always −2. Hydrogen is +1, except in metal hydrides, where it is −1. Others vary: iron is +2 or +3, sulfur is −2, +4 or +6, and chlorine runs from −1 up to +7.

In a neutral compound the oxidation states add up to zero. In water, two hydrogens at +1 balance one oxygen at −2. In a charged ion they add up to the charge: in the sulfate ion, sulfur at +6 and four oxygens at −2 each give a total of −2.

Electron configuration

An electron configuration says which orbitals an atom’s electrons occupy. Each entry is a number for the shell, a letter for the orbital type (s, p, d or f) and a small number for how many electrons sit there. The cards use the short form, which starts with the nearest noble gas in square brackets to stand for the inner electrons.

Sodium is [Ne] 3s¹: the full neon core plus one electron in the 3s orbital, which explains why it loses that single electron so easily and forms Na⁺. Chlorine is [Ne] 3s² 3p⁵, one electron short of a full 3p orbital, which is why it readily gains one and forms Cl⁻. Iron is [Ar] 3d⁶ 4s².

Orbitals generally fill in a set order: 1s, 2s, 2p, 3s, 3p, 4s, 3d and so on. A few elements break the pattern because half-filled and full d orbitals are especially stable. Chromium is [Ar] 3d⁵ 4s¹ and copper is [Ar] 3d¹⁰ 4s¹, not the 4s² you might expect.

Solid, liquid or gas at 77 °F

Choose the state color mode to see each element at room temperature, 77 °F (25 °C). Eleven elements are gases: hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon and radon. Only two are liquids: bromine and mercury. The rest are solids.

Two metals come close to being liquid. Cesium melts at about 83 °F (28.5 °C) and gallium at about 86 °F (29.8 °C), so on a warm day either one is close to melting. Gallium famously melts in a warm hand; cesium reacts violently with air and water and is never handled. For the heaviest, short-lived elements, from element 100 on, the state is shown as unknown, because they have never been made in large enough amounts to observe.

Frequently asked questions

How many elements are in the periodic table?

There are 118, from hydrogen (1) to oganesson (118). Almost all of the elements up to uranium (92) occur in nature; the heavier ones were first made in laboratories. The four most recent, nihonium, moscovium, tennessine and oganesson, were officially named in 2016.

What is the difference between a group and a period?

A group is a column, numbered 1 to 18, and a period is a row, numbered 1 to 7. Elements in a group share similar chemistry; elements in a period share the same number of electron shells. See all 18 groups and their families on the periodic table groups page.

What does the atomic number tell you?

It is the number of protons in the nucleus, and it is what defines the element: every atom with 8 protons is oxygen. In a neutral atom the number of electrons is the same.

Which element is the most electronegative?

Fluorine, at 3.98 on the Pauling scale. Among the elements with a listed value, the lowest belong to the heavy alkali metals, cesium and francium.

Yes. Open an element and copy the address from your browser: it ends with # and the symbol, for example #fe for iron. Search accepts the symbol, the name or the atomic number, and both American and British spellings, so aluminum and aluminium find the same card.