halogen

American  

[hal-uh-juhn, -jen, hey-luh-] / ˈhæl ə dʒən, -ˌdʒɛn, ˈheɪ lə- /

noun

Chemistry.

1. any of the electronegative elements, fluorine, chlorine, iodine, bromine, and astatine, that form binary salts by direct union with metals.

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halogen British  

/ ˈhæləˌdʒɛn, həˈlɒdʒɪnəs /

noun

1. any of the chemical elements fluorine, chlorine, bromine, iodine, and astatine. They are all monovalent and readily form negative ions

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halogen Scientific  

/ hăl′ə-jən /

1. Any of a group of five nonmetallic elements with similar properties. The halogens are fluorine, chlorine, bromine, iodine, and astatine. Because they are missing an electron from their outermost shell, they react readily with most metals to form salts.

2. See Periodic Table

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Other Word Forms

• halogenoid adjective
• halogenous adjective

Etymology

Origin of halogen

First recorded in 1835–45; halo- + -gen

Compare meaning

How does halogen compare to similar and commonly confused words? Explore the most common comparisons:

• halide vs. halogen

Explanation

A halogen is a chemical element that forms a salt when it reacts with metal. Halogen lamps are illuminated by bulbs that contain a halogen and an inert gas. There are five halogens in the periodic table of chemical elements: fluorine, chlorine, bromine, iodine, and astatine. The halogens are all highly reactive, which means they're quick to form bonds with other elements. What they often end up becoming is some kind of salt, including common table salt. In fact, the literal translation of halogen is "salt-producer," from Greek roots hals, "salt," and gen, "giving birth to."

Example Sentences

This process allows researchers to control which halogen atoms, including chlorine, bromine, or iodine, attach to the surface.

From Science Daily • Apr. 4, 2026

Another problem is the illegal retrofitting of LED bulbs, especially when fitted into units designed for halogen.

From BBC • Feb. 18, 2026

The housing for halogen bulbs is not compatible with LED bulbs, and a retrofitted car will not pass its annual MOT check-up.

From BBC • Oct. 27, 2025

Furthermore, to elucidate the role of the halogen bonds in the above-mentioned photoinduced sequential dynamics, the researchers conducted quantum chemistry calculations using the ultrafast electron diffraction results.

From Science Daily • Jun. 4, 2024

The halogen bulbs were still installed, but the wires had come loose during Artemis’s investigations.

From "Artemis Fowl" by Eoin Colfer

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