定义Definition
卤化物是卤素（F、Cl、Br、I）与电负性较小的元素组成的二元化合物，也指卤离子 F⁻、Cl⁻、Br⁻、I⁻。金属卤化物多为离子化合物（如 NaCl、KBr），非金属卤化物多为共价分子（如 CCl₄、PCl₃）。有机卤化物又称卤代烃。
A halide is a binary compound of a halogen (F, Cl, Br, I) with a less electronegative element; the word also means the halide ions F⁻, Cl⁻, Br⁻ and I⁻. Metal halides are mostly ionic (NaCl, KBr), while non-metal halides are mostly covalent molecules (CCl₄, PCl₃). Organic halides are halogenoalkanes and their relatives.
卤离子的检验Testing for halide ions
用稀硝酸酸化后加硝酸银溶液：Cl⁻ 生成白色 AgCl，Br⁻ 生成奶油色 AgBr，I⁻ 生成黄色 AgI；再用氨水区分：AgCl 溶于稀氨水，AgBr 溶于浓氨水，AgI 不溶。
Acidify with dilute nitric acid and add silver nitrate: Cl⁻ gives white AgCl, Br⁻ cream AgBr and I⁻ yellow AgI. Ammonia then distinguishes them: AgCl dissolves in dilute ammonia, AgBr in concentrated ammonia, and AgI not at all.
与浓硫酸反应的递变Trend with concentrated sulfuric acid
NaCl 只生成 HCl；NaBr 生成的 HBr 部分被氧化为 Br₂，硫酸被还原为 SO₂；NaI 生成的 HI 进一步把硫酸还原为 S 和 H₂S，析出碘。说明卤离子的还原性 I⁻ > Br⁻ > Cl⁻。
NaCl gives only HCl; with NaBr some HBr is oxidised to Br₂ while the acid is reduced to SO₂; with NaI the HI reduces the acid further to S and H₂S and iodine forms. This shows reducing power I⁻ > Br⁻ > Cl⁻.