Name: fluorine
Symbol: F
Atomic number: 9
Atomic weight: 18.9984032 (5)
CAS Registry ID: 7782-41-4
Group number: 17
Group name: Halogen
Period number: 2
Block: p-block
Group
number: 17
Group name: Halogen
Period number: 2
Block: p-blockBrief
description of fluorine.
Standard
state: gas at 298 K
Colour: pale yellow
Classification: Non-metallic
Availability:
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and safely packaged collection of the 92 naturally occurring
elements that is available for sale.
Fluorine
is a Group 17 element. Fluorine is the most electronegative
and reactive of all elements. It is a pale yellow, corrosive
gas, which reacts with practically all organic and inorganic
substances. Finely divided metals, glass, ceramics, carbon,
and even water burn in fluorine with a bright flame.
Until World War 2, there was no commercial production
of elemental fluorine. Atom bomb projects and nuclear
energy applications made it necessary to produce large
quantities of fluorine since isotopes of uranium can
be separated through the gas diffusion of UF6. Reasonably
safe handling techniques for fluorine are now available
and one can transport liquid fluorine by the ton. Compounds
of fluorine with noble gases such as xenon, radon, and
krypton are known. Elemental fluorine and the fluoride
ion (in quantity) are highly toxic.
Isolation
Here is a brief summary of the isolation of fluorine.
It would never be necessary to make fluorine gas in most laboratories. Fluorine
is available commercially in cylinders but is very difficult to handle. Fluorine
may be recovered with difficulty as a highly reactive and corrosive pale yellow
gas by electrolysis of hot molten mixtures (1:2) of potassium fluoride (KF) and
hydrogen fluoride (HF). The electrolyte is corrosive, so is the product. Grease
must be avoided because of the fire hazard. It is difficult to store as it reacts
with most materials but steel and Monel metal containers may be used as the metal
surfaces deactivate through the formation of unreactive surface fluorides.
Fluorine
Electronic
Configuration
The following represents the electronic configuration and its associated term
symbol for the ground state neutral gaseous atom. The configuration associated
with fluorine in its compounds is not necessarily the same.
Ground
state electron configuration: [He].2s2.2p5
Shell structure: 2.7
Term symbol: 2P3/2
What's in a name? From the Latin and
French words for flow, fluere.
Say what? Fluorine is pronounced as FLU-eh-reen or as FLU-eh-rin.
History and Uses:
Fluorine is the most reactive of all elements and no chemical substance is
capable of freeing fluorine from any of its compounds. For this reason, fluorine
does not occur free in nature and was extremely difficult for scientists to
isolate. The first recorded use of a fluorine compound dates to around 1670
to a set of instructions for etching glass that called for Bohemian emerald
(CaF2). Chemists attempted to identify the material that was capable of etching
glass and George Gore was able to produce a small amount of fluorine through
an electrolytic process in 1869. Unknown to Gore, fluorine gas explosively
combines with hydrogen gas. That is exactly what happened in Gore's experiment
when the fluorine gas that formed on one electrode combined with the hydrogen
gas that formed on the other electrode. Ferdinand Frederic Henri Moissan, a
French chemist, was the first to successfully isolate fluorine in 1886. He
did this through the electrolysis of potassium fluoride (KF) and hydrofluoric
acid (HF). He also completely isolated the fluorine gas from the hydrogen gas
and he built his electrolysis device completely from platinum. His work was
so impressive that he was awarded the Nobel Prize for chemistry in 1906. Today,
fluorine is still produced through the electrolysis of potassium fluoride and
hydrofluoric acid as well as through the electrolysis of molten potassium acid
fluoride (KHF2).
Fluorine
is added to city water supplies in the proportion of
about one part per million to help prevent tooth decay.
Sodium fluoride (NaF), stannous(II) fluoride (SnF2) and
sodium monofluorophosphate (Na2PO3F) are all fluorine
compounds added to toothpaste, also to help prevent tooth
decay. Hydrofluoric acid (HF) is used to etch glass,
including most of the glass used in light bulbs. Uranium
hexafluoride (UF6) is used to separate isotopes of uranium.
Crystals of calcium fluoride (CaF2), also known as fluorite
and fluorspar, are used to make lenses to focus infrared
light. Fluorine joins with carbon to form a class of
compounds known as fluorocarbons. Some of these compounds,
such as dichlorodifluoromethane (CF2Cl2), were widely
used in air conditioning and refrigeration systems and
in aerosol spray cans, but have been phased out due to
the damage they were causing to the earth's ozone layer.
Estimated Crustal Abundance: 5.85×102 milligrams per kilogram
Estimated Oceanic Abundance: 1.3 milligrams per liter
Number of Stable Isotopes: 1 (View all isotope data)
Ionization Energy: 17.423 eV
Oxidation State: -1
Discovery
Fluorine was first identified by Scheele in 1771AD.
Fluorine was first isolated by Moissan in 1886AD, when he noted the inclusion
of fluorine in crystals of fluorspar from Quincie.
Occurrence
Fluorine is an element which widely distributed, but not very abundant. However,
because of its high reactivity is not found naturally in its elemental state.
Fluorine
occurs in
Cryolite, Na3AlF6,
Fluorspar, CaF2, and
Fluorapatite, 3Ca3(PO4)2.Ca(ClF).
Extraction
Preparation
Fluorine can be prepared by the electrolysis of fused acid potassium fluoride
at 373 degK in a copper vessel using graphite electrodes. The electrolyte,
pure and dry acid potassium fluoride is fused in an electrically heated
vessel, such as a wide copper V-tube, the electrodes are pure acheson graphite
rods insulated in bakelite cement stoppers. A current of 5 amperes at 12
volts is used. The fluorine is purified by passage through two copper U-tubes,
containing dry sodium fluoride.
Manufacture
Fluorine is made on the industrial scale by the electrolysis of fused acid
potassium fluoride in a copper vessel using graphite electrodes at currents
up to 2,000 amperes. An anode current efficiency of about 95% was attained.
The fluorine gas is then piped in steel or copper vessels and compressed
up to 400 lb/in2 in nickel and steel cylinders.
Properties
Fluorine is a light canary-yellow gas at room temperature.
Fluorine is the most reactive and electronegative of all elements.
Reactions
Fluorine reacts explosively with hydrogen even in the dark and at low temperature.
Fluorine reacts violently with water forming hydrogen fluoride, and liberates
oxygen which is highly charged with ozone.
2 F2 + 2 H2O ==> 4 HF + O2
Fluorine
also reacts with sulphur, selenium, and tellurium, which
melt and ignite in the gas, forming halides.
Fluorine is a powerful oxidising agent. For example, when fluorine is bubbles
through a solution of potassium chlorate this is oxidised to potassium perchlorate.
F2 + 2 KClO3 + H2O ==> 2 HF + KClO4
Fluorine
does not react directly with oxygen, or nitrogen, and
combines with chlorine, only on heating, forming the
gaseous products chlorine fluoride, and chlorine trifluoride.
Fluorine readily combines with bromine, and iodine, forming colourless liquids
BrF3 and IF5.
Uses
Fluorine is used in the synthesis of organic fluorine compounds.
Fluorine is used in the manufacture of Freon (i.e. dichlorodifluoromethane,
CCl2F2) which is used as a refrigerant.
Fluorine
is used in the manufacture of uranium hexafluoride which
is required for the separation of the isotopes of uranium
in centrifuges.
Detection and
Analysis
Fluorine is detected by its corrosive action on glass (i.e. the glass is etched). |
