Definition

1. Noun:
   • A group of reactive nonmetallic elements: "Halogen" refers to any of the five chemically related elements in Group 17 of the periodic table: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). They are all monovalent (typically forming one bond) and readily gain an electron to form negative ions (anions).

Usage and Examples

• Noun:
  • Chlorine, a common halogen, is used to disinfect swimming pools.
  • The reactivity of the halogen decreases as you move down the group in the periodic table.
  • Iodine is a halogen essential for thyroid function in humans.

Advanced Usage

• "Halogen lamp": A type of incandescent lamp containing a halogen gas, which allows the filament to operate at a higher temperature, producing a brighter, whiter light.
  • The living room was brightly lit by a modern halogen lamp.

Variants and Related Words

• Halogenate (verb): To introduce a halogen atom into a compound.
  • Scientists can halogenate organic molecules to alter their properties.
• Halogenation (noun): The chemical process of adding a halogen to a substance.
  • The halogenation of methane produces methyl chloride.

Synonyms

• Group 17 elements: The formal designation for halogens in the periodic table.
• Salt-formers: A descriptive term, as halogens readily form salts (like sodium chloride) with metals.

Related Phrases and Compounds

• Halogen bond: A type of non-covalent interaction similar to a hydrogen bond, involving a halogen atom.
  • Halogen bonds can influence the structure of certain crystals.
• Halogen-free: A label for materials that do not contain halogens, often important for safety and environmental standards.
  • This wiring insulation is halogen-free to reduce toxic fumes in a fire.

Notes on Meaning

The term "halogen" specifically denotes this defined group of five elements. While they share common properties, their physical states at room temperature vary: fluorine and chlorine are gases, bromine is a liquid, and iodine and astatine are solids. Astatine is radioactive and very rare.

Noun

1. any of five related nonmetallic elements (fluorine or chlorine or bromine or iodine or astatine) that are all monovalent and readily form negative ions