The halogens are a group of highly reactive nonmetallic elements found in Group 17 (also called Group VIIA) of the periodic table. The name "halogen" comes from Greek words meaning "salt-former," because these elements readily form salts when they react with metals.
Members of the Halogen Group:
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Fluorine (F)
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Chlorine (Cl)
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Bromine (Br)
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Iodine (I)
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Astatine (At) – a rare and radioactive element
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Tennessine (Ts) – a synthetic element with very limited data
General Properties:
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Electronic Configuration: ns² np⁵ (7 valence electrons)
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Oxidation State: Commonly -1, but can show positive oxidation states in some compounds
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Physical State at Room Temperature:
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Fluorine: pale yellow gas
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Chlorine: greenish-yellow gas
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Bromine: reddish-brown liquid
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Iodine: violet solid
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Astatine: solid (radioactive)
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Reactivity: Extremely reactive, especially fluorine; reactivity decreases down the group
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Electronegativity: Very high; fluorine is the most electronegative element
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Toxicity: Most halogens are toxic and must be handled with care
Chemical Properties:
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Strong oxidizing agents
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Form halide ions (X⁻) by gaining one electron
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React vigorously with metals to form ionic halides (e.g., NaCl)
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Form covalent compounds with nonmetals
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Participate in displacement reactions (more reactive halogen displaces a less reactive one from its compound)
Uses:
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Chlorine: Water purification, PVC production
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Fluorine: Toothpaste (fluorides), Teflon manufacture
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Bromine: Flame retardants, photography
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Iodine: Antiseptics, nutritional supplements
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Astatine and Tennessine: Mostly used in scientific research due to rarity and radioactivity
Summary:
Halogens are essential yet dangerous elements, known for their strong reactivity and salt-forming ability. Their compounds are widely used in industry, medicine, and daily life, making them a crucial group in chemistry.
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