定义Definition
氟是第 9 号元素，符号 F，位于第二周期第 17 族，是电负性最大（3.98）的元素。单质氟 F₂ 是淡黄色有毒气体，是已知最强的氧化剂之一，几乎能与所有元素反应。
Fluorine is element 9, symbol F, in period 2 and group 17, and the most electronegative element (3.98). The element, F₂, is a pale yellow toxic gas and one of the strongest oxidising agents known, reacting with almost every element.
元素数据Element data
| 原子序数Atomic number | 9 |
|---|---|
| 元素符号Symbol | F |
| 相对原子质量Standard atomic weight | 18.998 |
| 电子排布Electron configuration | [He] 2s² 2p⁵ |
| 族 / 周期 / 区Group / period / block | 17 / 2 / p |
| 电负性（鲍林）Electronegativity (Pauling) | 3.98 |
| 常见氧化态Common oxidation states | −1 |
特殊性Why fluorine is unusual
氟原子很小，F–F 键能只有约 158 kJ mol⁻¹，比 Cl–Cl（243 kJ mol⁻¹）还弱，因为两个小原子上的孤对电子相互排斥；同时氟与其他元素形成的键很强。这两点使氟极其活泼。氟在化合物中只有 −1 价。HF 分子间形成强氢键，沸点（19.5 °C）反常地高，在水中是弱酸，但能腐蚀玻璃：SiO₂ + 4HF → SiF₄ + 2H₂O。
The fluorine atom is small and the F–F bond energy is only about 158 kJ mol⁻¹, weaker than Cl–Cl (243 kJ mol⁻¹), because lone pairs on the two small atoms repel; at the same time fluorine forms very strong bonds to other elements. Together these make it extremely reactive. In compounds fluorine is always −1. HF molecules hydrogen-bond strongly, so HF boils unusually high (19.5 °C); it is a weak acid in water but attacks glass: SiO₂ + 4HF → SiF₄ + 2H₂O.
制备与用途Production and uses
氟气由电解熔融 KF·HF 混合物制得。氟用于制造 UF₆（铀同位素分离）、聚四氟乙烯、含氟制冷剂和药物；牙膏中的氟化物使牙釉质转化为更耐酸的氟磷灰石。
Fluorine gas is made by electrolysing molten KF·HF. It is used for UF₆ (uranium enrichment), PTFE, fluorinated refrigerants and drugs; fluoride in toothpaste turns tooth enamel into the more acid-resistant fluorapatite.
化学性质Chemical properties
与氢气在暗处即剧烈化合：H₂ + F₂ → 2HF
Combines explosively with hydrogen even in the dark: H₂ + F₂ → 2HF
使水释放氧气：2F₂ + 2H₂O → 4HF + O₂
Releases oxygen from water: 2F₂ + 2H₂O → 4HF + O₂
能与氙等稀有气体反应，如 Xe + 2F₂ → XeF₄
Reacts even with noble gases such as xenon: Xe + 2F₂ → XeF₄
年表Timeline
- 1810
安培提出氢氟酸中含有一种未知元素
Ampère suggests hydrofluoric acid contains an unknown element
- 1886
莫瓦桑电解制得单质氟
Moissan isolates fluorine by electrolysis
- 1906
莫瓦桑获诺贝尔化学奖
Moissan receives the Nobel Prize in Chemistry