Halogen — Definition, Formula, Properties & Uses | AllChemicals | AllChemicals

Q: What is the formula for Halogen?

The formula or notation for Halogen is: F₂, Cl₂, Br₂, I₂, At; Group 17; ns²np⁵ valence configuration

Formula / Notation	F₂, Cl₂, Br₂, I₂, At; Group 17; ns²np⁵ valence configuration
Also Known As	Group 17 elements, Group VIIA elements, halogens

What is Halogen?

Any of the Group 17 elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Halogens are highly reactive nonmetals that form -1 ions. They exist as diatomic molecules and are used in water purification, pharmaceuticals, and polymers.

Formula & Notation

F₂, Cl₂, Br₂, I₂, At; Group 17; ns²np⁵ valence configuration

Other Names / Synonyms: Group 17 elements, Group VIIA elements, halogens

Properties & Characteristics

Halogens are the Group 17 elements (F, Cl, Br, I, At, Ts) with valence configuration ns²np⁵. They are the most electronegative and reactive nonmetals. Halogens exist as diatomic molecules (X₂) at standard conditions; reactivity decreases F₂ > Cl₂ > Br₂ > I₂ (decreasing electronegativity and bond dissociation energy). They readily form halide ions (X⁻) with metals and covalent bonds with nonmetals. All are oxidising agents.

Uses & Applications

Halogens are used in: water disinfection (Cl₂, ClO₂, NaOCl, chloramine), bleaching (Cl₂, NaOCl in paper/textile), pharmaceuticals (F and Cl in most drugs to enhance metabolic stability), PVC production (Cl₂), photography (AgBr, AgI as light-sensitive salts), and laboratory synthesis.

Safety Information

All halogens are toxic oxidising gases or vapours. F₂ and Cl₂ are acutely toxic at ppm levels (IDLH: F₂ = 25 ppm, Cl₂ = 10 ppm). Bromine is a corrosive liquid. Iodine is a solid that sublimes; vapour irritates mucous membranes. Use halogens only in fume hoods with appropriate gas detectors.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Halogen

Formula F₂, Cl₂, Br₂, I₂, At; Group 17; ns²np⁵ valence configuration

Index All "H" terms

Synonyms Group 17 elements, Group VIIA elements, halogens

Frequently Asked Questions

What is Halogen?

Any of the Group 17 elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Halogens are highly reactive nonmetals that form -1 ions. They exist as diatomic molecules and are used in water purification, pharmaceuticals, and polymers.

What is Halogen used for?

Is Halogen hazardous?

What is the formula for Halogen?

More "H" Terms

Haber Process N₂ + 3H₂ ⇌ 2NH₃ | ΔH = −92 kJ/mol Hafnium Hf Half Cell Half Life Half-Cell E = E° − (RT/nF)lnQ Half-Life A(t) = A₀e^(−λt); t½ = ln2/λ Half-Reaction Halide X⁻ (e.g., F⁻, Cl⁻, Br⁻, I⁻) Halogenation C-X + Cl₂/Br₂ (hv or AlCl₃) → C-X(halogen); EAS or radical pathway Halogens Hard Acid Hard acid: small, highly charged, low polarisability (e.g., H⁺, Mg²⁺, Al³⁺) Hard Base Hard base: high EN, low polarisability (e.g., F⁻, OH⁻, NH₃, H₂O)

View all "H" terms →