Interactive periodic table of the elements
Explore all 118 chemical elements in this interactive periodic table. Each tile shows the element’s symbol and atomic number, colour-coded by category — alkali metals, transition metals, halogens, noble gases, and more. Click any element to see its full name, atomic number, atomic mass, group, and period.
How the periodic table is organised
Elements are arranged by increasing atomic number into rows called periods and columns called groups. Elements in the same group share similar chemical properties because they have the same number of outer electrons. The two separate rows at the bottom are the lanthanides and actinides (the f-block), which are pulled out to keep the table compact.
Using it with our other tools
The atomic masses shown here are exactly what you need for the molecular weight calculator. To compare how strongly elements attract electrons and predict bonding, try the electronegativity calculator, and for solution work see the chemistry calculator.
Frequently asked questions
How many elements are there?
There are 118 confirmed elements, from hydrogen (1) to oganesson (118). The first 94 occur naturally, while the rest have only been made artificially.
What do the groups mean?
Groups are the vertical columns (1–18). Elements in a group have similar properties — for example, Group 1 are reactive alkali metals and Group 18 are unreactive noble gases.
Why are the lanthanides and actinides shown separately?
Purely for convenience. They belong in periods 6 and 7, between groups 2 and 3, but including them in the main body would make the table 32 columns wide. Pulling them out keeps the table readable on a page or screen.
Why are some atomic masses whole numbers?
Elements such as technetium, promethium and everything beyond uranium have no stable isotopes, so there is no natural average to quote. For these, the table shows the mass number of the longest-lived known isotope instead.
How to read an element tile
Each tile packs three key facts. The small number is the atomic number, which is the number of protons in the nucleus and the element’s unique identity: every atom with 6 protons is carbon. The large letters are the chemical symbol, usually taken from the English or Latin name (Fe for iron comes from the Latin ferrum). Click a tile and you will also see the relative atomic mass, a weighted average of the masses of the element’s natural isotopes, measured in atomic mass units (u).
The atomic number also tells you the number of electrons in a neutral atom. Subtracting the atomic number from the mass number of a specific isotope gives the number of neutrons. For example, carbon-12 has 6 protons and 12 − 6 = 6 neutrons, while carbon-14 has 8 neutrons.
The four blocks: s, p, d and f
The table’s shape comes from the way electrons fill their orbitals. Chemists divide it into four blocks named after the orbital being filled in each region.
| Block | Location | Typical elements |
|---|---|---|
| s-block | Groups 1 and 2, plus helium | Sodium, potassium, calcium, magnesium |
| p-block | Groups 13 to 18 | Carbon, oxygen, chlorine, neon |
| d-block | Groups 3 to 12 | Iron, copper, silver, gold |
| f-block | Lanthanides and actinides | Neodymium, uranium, plutonium |
For a fuller walkthrough with UK and US group numbering and a method for placing any element from its atomic number, read our guide to reading the periodic table: groups, periods and blocks.
Periodic trends
Because the table is ordered by electron structure, many properties change in predictable ways as you move across a period or down a group. Learning these trends lets you predict how an unfamiliar element will behave.
- Atomic radius decreases from left to right across a period, as the growing nuclear charge pulls electrons closer, and increases down a group as new electron shells are added.
- Ionisation energy, the energy needed to remove an outer electron, generally increases across a period and decreases down a group. That is why the alkali metals at the bottom of Group 1 are so reactive.
- Electronegativity, an atom’s pull on shared electrons, increases across a period and decreases down a group. Fluorine is the most electronegative element, with a Pauling value of 3.98.
- Metallic character increases down and to the left. Metals sit on the left and centre, non-metals on the upper right, and the metalloids such as silicon and germanium form a staircase between them.
Worked example: finding the molar mass of water
Click hydrogen and oxygen in the table above to read their atomic masses: H = 1.008 u and O = 15.999 u. A water molecule, H₂O, contains two hydrogen atoms and one oxygen atom.
- Hydrogen: 2 × 1.008 = 2.016
- Oxygen: 1 × 15.999 = 15.999
- Total: 2.016 + 15.999 = 18.015 g/mol
So one mole of water has a mass of about 18.02 g. The molecular weight calculator does this automatically for any formula, including brackets and hydrates, and our guide on how to calculate molecular weight shows more examples.
A brief history
In 1869 the Russian chemist Dmitri Mendeleev arranged the 63 elements then known by atomic mass and chemical behaviour, leaving gaps for elements he predicted would be discovered. Gallium (1875), scandium (1879) and germanium (1886) later filled those gaps with properties very close to his predictions. In 1913 Henry Moseley showed that atomic number, not mass, is the true ordering principle. The seventh period was completed in 2016, when IUPAC approved the names nihonium, moscovium, tennessine and oganesson for elements 113, 115, 117 and 118.
For related tools, see the science tools hub, the solution dilution calculator and the scientific notation converter.