Interactive Periodic Table of Elements
Click any element for full properties, isotopes, trends — and research-grade chemicals with COA & SDS.
The periodic table organizes all 118 confirmed chemical elements by atomic number into 18 groups and 7 periods. Elements in the same group share valence-electron configurations and behave similarly. IUPAC last revised the standard atomic weights in 2021; the four newest elements (Nh, Mc, Ts, Og) were confirmed in 2016.
How the periodic table is organized
Dmitri Mendeleev published the first widely adopted periodic table in 1869, ordering the ~60 elements then known by atomic weight and leaving deliberate gaps for elements he predicted — gallium and germanium were later discovered with almost exactly the properties he forecast. The modern table orders elements by atomic number (proton count) instead, following Henry Moseley's 1913 X-ray work, which resolved the inconsistencies in Mendeleev's weight-based ordering.
Position encodes structure: the row (period) tells you how many electron shells an atom has, and the column (group) tells you how its outermost shell is filled. That is why sodium and potassium — same group, different periods — both react violently with water, and why the noble gases in group 18 barely react at all.
Who updates the periodic table?
The International Union of Pure and Applied Chemistry (IUPAC) validates new element discoveries, approves names and symbols, and revises the standard atomic weights as isotopic measurements improve — most recently in 2021. Period 7 was completed in 2016 with nihonium (113), moscovium (115), tennessine (117), and oganesson (118).
How element properties vary across the table
Atomic radius decreases across a period (rising nuclear charge pulls electrons inward) and increases down a group (each period adds a shell). Ionization energy and electronegativity follow the opposite pattern, peaking at fluorine (3.98 Pauling). Metallic character strengthens toward the lower left — cesium and francium are the most reactive metals; fluorine and oxygen the most reactive nonmetals. Use the Display Property/Trend selector above to color the table by any of 13 properties, from atomic mass to year discovered.
Frequently asked questions
How many elements are in the periodic table?
The periodic table contains 118 confirmed elements. Ninety-four occur naturally on Earth; the remainder are synthetic. The four most recently confirmed — nihonium, moscovium, tennessine, and oganesson — were formally added by IUPAC in 2016, completing period 7.
What do the groups and periods of the periodic table mean?
The 18 vertical columns are groups: elements in a group share the same number of valence electrons and therefore similar chemical behavior. The 7 horizontal rows are periods: each period adds a new electron shell, so atomic radius grows down a group and shrinks across a period.
Who maintains and updates the periodic table?
The International Union of Pure and Applied Chemistry (IUPAC) verifies element discoveries, approves names and symbols, and periodically revises the standard atomic weights; the most recent revision was published in 2021.
Why do some elements show an atomic mass in brackets?
Elements with no stable isotopes — such as technetium (Tc, 98) and all elements beyond uranium — have no fixed natural atomic weight. The bracketed value is the mass number of the longest-lived or most important isotope.
How does electronegativity change across the periodic table?
Electronegativity increases left to right across a period and decreases down a group. Fluorine is the most electronegative element (3.98 on the Pauling scale); francium and cesium are the least (about 0.7).
About this data: property values compiled from IUPAC Standard Atomic Weights (2021), the NIST Atomic Spectra Database, and PubChem. Curated by the Aladdin Scientific technical team. Last reviewed: .