Periodic Table Viewer
The table, with everything behind it
Search or filter all 118 elements by category, and read atomic mass, electron configuration, phase and discovery date.
Periodic Table Viewer
Runs in your browser · nothing uploadedOne or two letters is read as a symbol, so “C” finds carbon rather than every name containing the letter. 118 of 118 elements.
Iron
Transition metal
- Configuration
- [Ar] 3d6 4s2
- Phase at 20 °C
- Solid
- Period · group
- 4 · 8
- Discovered
- c. 5,000 BCE
Click an element for its details · arrow keys move across the table · hover a category to see where it sits.
01 — How to use Periodic Table Viewer
02 — Getting good results
03 — Questions
Standard atomic weights follow IUPAC recommendations. Categories, groups, periods and electron configurations are the conventional values found in any reference table. Everything ships inside the page — nothing is fetched.
Because they have barely existed. The elements past meitnerium have been produced only a few atoms at a time, with half-lives measured in seconds or less, which is not enough material to determine chemical behaviour experimentally. Their placement in the table is predicted from their position rather than observed.
It is the IUPAC spelling, and this site uses British English throughout. Sulfur, by contrast, is spelled with an f here, which is also the IUPAC form and has been the recommended spelling in the UK since 1992.
None confirmed. Element 118, oganesson, completes the seventh period. Attempts to synthesise 119 and 120 are ongoing, and if either is confirmed the table gains an eighth period.
04 — More about Periodic Table Viewer
What the table is actually organised by
The periodic table arranges elements by atomic number — the count of protons in the nucleus — and the rows and columns are not arbitrary. A period corresponds to an electron shell being filled, and a group collects elements whose outermost shell has the same number of electrons. That shared outer structure is why elements in a group behave alike: the noble gases in group 18 are unreactive because their outer shells are complete, and the alkali metals in group 1 are violently reactive because each has a single loosely held electron it is eager to lose. Mendeleev arranged the table by observed properties before any of this was understood, and left gaps where the pattern demanded an element nobody had found. Gallium, scandium and germanium were later discovered with close to the properties he predicted.
Atomic weight is an average, not a count
The mass shown for a stable element is a standard atomic weight: a weighted average of the masses of its naturally occurring isotopes, in the proportions they are found on Earth. This is why chlorine is 35.45 rather than a whole number — it is roughly three parts chlorine-35 to one part chlorine-37. The averaging also means the figure is not universal: the isotopic mixture of an element can vary slightly by source, which is why IUPAC now publishes intervals rather than single values for several elements. For elements with no stable isotope the concept does not apply at all, since there is no natural mixture to average, and the mass number of the longest-lived isotope is quoted instead.
The lanthanides, the actinides, and the shape of the table
The two rows usually printed below the main body are not a footnote; they belong in the middle of periods six and seven, between groups 2 and 3. They are separated for a purely practical reason: including them inline makes the table about half as wide again, which does not fit comfortably on a page. This tool sidesteps the problem by presenting the elements as a list rather than as the familiar grid, which loses the visual relationships the grid encodes but gains the ability to sort and search — a different set of trade-offs for a different set of questions.
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