Periodic Table of Elements

Click any element to view full details · Search or filter to explore all 118 elements

Lanthanides (57–71)
Actinides (89–103)
Alkali Metal Alkaline Earth Metal Transition Metal Post-transition Metal Metalloid Nonmetal Halogen Noble Gas Lanthanide Actinide Unknown

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Jump into the quiz below and test your knowledge of the periodic table — three modes, instant scoring.

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Element Comparison

Select up to three elements from the periodic table above (tap ⇄ Compare on any element) to see them side by side across fourteen properties.

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How the Periodic Table Works

A quick reference for students: the history behind the table, how to read it, and the vocabulary chemists use every day.

Periodic Table History

Dmitri Mendeleev published the first widely recognized periodic table in 1869, arranging known elements by atomic weight and leaving gaps for elements yet to be discovered. Later, Henry Moseley's work on atomic number gave the table its modern ordering principle.

How to Read the Table

Each cell shows an element's atomic number, symbol, name, and atomic mass. Rows are periods, columns are groups. Color indicates chemical category — metals on the left, nonmetals on the right, metalloids along the dividing line.

Atomic Structure

Every atom has a nucleus of protons and neutrons surrounded by electrons arranged in shells. The number of protons defines the element; the arrangement of outer electrons determines how it reacts with others.

Groups Explained

A group is a vertical column of 18. Elements in the same group share the same number of valence electrons, giving them similar chemical behavior — for example, Group 1 alkali metals all react vigorously with water.

Periods Explained

A period is a horizontal row. Moving across a period, atomic number increases by one each step and electrons fill the same outer shell, gradually changing the element's properties from metallic to nonmetallic.

Blocks Explained

The table is divided into s, p, d, and f blocks based on which electron subshell is being filled last. The f-block elements — lanthanides and actinides — are pulled out below the main table purely to keep it a manageable width.

Common Chemistry Terms

A measure of how strongly an atom attracts shared electrons in a chemical bond. Fluorine has the highest electronegativity of any element.
The weighted average mass of an element's naturally occurring isotopes, measured in atomic mass units (u).
Metals are typically shiny, conductive, and malleable. Nonmetals are poor conductors and often gases or brittle solids. Metalloids sit on the dividing line and share properties of both.
Elements heavier than lead generally have nuclei too large to stay stable indefinitely, so they undergo radioactive decay. Some lighter elements, like technetium, are also exclusively radioactive.
Synthetic elements are produced artificially in laboratories, usually by colliding lighter nuclei together, because they don't occur in measurable quantities in nature.
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Chemistry Calculators

Three quick tools: look up atomic mass, calculate molecular weight from a formula, and inspect electron configurations.

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