halogen

American  

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

noun

Chemistry.

• halogens
  plural

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 /

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

Derived Forms

• halogenoid
  adjective
• halogenous
  adjective

Inflected Forms

Nouns

• halogens
  plural

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Etymology

Origin of halogen

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

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Compare meaning

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

• halide vs. halogen

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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

See Examples For:

halogen halogens

He did a more-than-competent job—he was Rossini after all—but the result always reminds me of shining a halogen light into a place of hallowed dim.

From The Wall Street Journal ● May 15, 2026

"The resulting datasets are producing an improved understanding of the interactions between sea-spray aerosols, surface-coupled clouds, oil field emissions and multiphase halogen chemistry in the new Arctic."

From Science Daily ● Dec. 29, 2025

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

One already well-understood source of glare is drivers retrofitting their vehicles, replacing old halogen bulbs with LEDs.

From BBC ● Oct. 27, 2025

As the broiling sun set, a different kind of American landscape lit up: The halogen floodlights from the truck stop could be seen for miles.

From "Geeks: How Two Lost Boys Rode the Internet Out of Idaho" by Jon Katz

The researchers now want to investigate ways to confine the molten salts, potentially using halogens or carbon-based materials, which could make the salts easier to separate and process while improving their stability.

From Science Daily ● Sep. 21, 2026

Firstly, they are two to three times as bright as traditional halogens, and their "colour temperature" is bluer and whiter, which mimics natural daylight.

From BBC ● Feb. 18, 2026

Researchers also found that halogens interact with oil field emissions to form free radicals, which later become more stable compounds capable of traveling long distances.

From Science Daily ● Dec. 29, 2025

Silicon reacts with halogens at high temperatures, forming volatile tetrahalides, such as SiF4.

From Textbooks ● Feb. 14, 2019

When heated with the halogens, acetophenone is substituted in the aliphatic portion of the nucleus; thus bromine gives phenacyl bromide, C6H6CO.CH2Br.

From The Project Gutenberg Encyclopedia Volume 1 of 28 by Project Gutenberg

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