|
History and Production
From Latin fluere, flowing which is related to the early use of fluorspar (CaF2). Due to the extreme reactivity nature of the element, many attempts had been made to isolate the gas, some ended in tragedy. In 1886, H. Moissan finally isolated fluorine by electrolysis of potassium hydrogen fluoride/hydrogen fluoride, after over 70 years of unsuccessful attempts by others.
He was later awarded the Nobel Prize for chemistry in 1906.
Nowadays, it is produced using methods based on Moissan's original procedure. The generator is made of a mild-steel pot (acting as cathode) while the anode consists of a central compacted, ungraphitized carbon rod.
Fluorine and its compounds are used in the production of uranium, high-temperature plastics, dielectrics. Hydrofluoric acid is used for glass etching. In the form of cryolite, Na3AlF6, it is used in the production of aluminium.
Physical Data
Fluorine is the most electronegative and reactive of all elements, hence the difficulty of isolation in the early years. It is a pale yellow, very corrosive gas which react practically with all organic and inorganic substances, including metals, glass (as shown above), ceramics, water etc., often with violent effects.
Fluorine has a pungent smell, even at a concentration of 20 ppb (parts per billion), which is below the safe working level. Fluorine occurs in nature mainly in the form of fluorite, CaF2, such as fluorspar (left) and fluorapatite, Ca5(PO4)3F. Cryolite is a rare mineral and is only
commercially available in Greenland. Cryolite that is used in the production of aluminium are in fact largely synthetic.
Interatomic distance: 141.8 pm
Melting point: -219.62°C
Boiling point: -188.12°C
Thermal conductivity/Wm-1K-1: 0.0279 (27°C)
Density/kgm-3: 1516 (b.p.), 1.696 (0°C)
Standard Thermodynamic Data (atomic gas)
Enthalpy of formation: 79.4 kJ/mol
Gibbs free energy of formation: 126.6 kJ/mol
Entropy: 62.3 J/mol K
Heat capacity: 22.7 J/mol K
Electronic data
Electronic configuration: [He] 2s2 2p5
Term symbol: 2P3/2
Electron affinity: 328.1651 kJ/mol Electronegativity (Pauline): 3.98
Ionization energy (first, second, third): 1681.05, 3374.17, 6050.45 kJ/mol
Chemical properties
Fluorine is the most reactive of all elements. Except helium, argon and neon, it forms compound with all other elements, often with violent effects.
The reactivity is due to its small size and that the dissociation energy of F-F bond is much smaller than the bonds that fluorine forms with other elements.
|
