Fluorine

[[File:Fluorine gas.jpeg|right|thumb|165px|
A fart in a bottle
 Fluorine in gaseous form.]]
{{Chemistry}}
'''Fluorine''' is the element of atomic number 9, the lightest of the halogens. Fluorine is an interesting element - it's extremely reactive, and it explodes a lot (in the right circumstances). It could be in your home, too! But in the slightly less dangerous form Teflon.

==Properties==
The properties of fluorine depend very much on which kind of compound it is a part of.

Pure fluorine is a greenish-yellow, extremely reactive, toxic gas.<ref>[https://pubchem.ncbi.nlm.nih.gov/compound/fluorine#section=Top Fluorine] PubChem: Open Chemistry Database</ref> Fluorine is incredibly reactive because its electronegativity is highest of all elements: its outermost electron shell has only a single hole in it, and it loves to pull any other electrons it can lay its hands on into said hole.<ref>[https://chem.libretexts.org/Textbook_Maps/Inorganic_Chemistry/Supplemental_Modules_(Inorganic_Chemistry)/Descriptive_Chemistry/Elements_Organized_by_Block/2_p-Block_Elements/Group_17%3A_The_Halogens/Z%3D009_Chemistry_of_Fluorine_(Z%3D9) Chemistry of Fluorine] LibreTexts: Chemistry</ref>

In covalent compounds, fluorine clings like a mofo to practically any molecule you bond it to. Its atomic radius is rather small, and its {{wpl|Carbon–fluorine bond|bond to carbon}} is "the strongest in organic chemistry". As a result, it can substitute hydrogen in organic compounds to form covalent organofluorine compounds, which are less reactive. This feature is what makes Teflon (polytetrafluoroethylene) nicely slippery and unreactive. Higher halogens, such as chlorine, are much less well-behaved. Light fluorocarbons are inert liquids and gases, useful as refrigerants. Fully fluorinated covalent fluorides, such as sulfur hexafluoride (SF<sub>6</sub>), are also very unreactive, and SF<sub>6</sub> is used for example to fill electrical transformers. The chemical industry likes fluorine because it makes nasty things like uranium much easier to work with: uranium hexafluoride is not a salt, like one would expect from a simple ionic compound, but a volatile, easily sublimed solid.

In pharmaceuticals, substitution of hydrogen with fluorine is particularly useful because it can block enzymes from digesting the molecule, which slows down its elimination from the body and increases potency. Furthermore, its electronegativity can be useful in its own right.

Fluorine can do neat tricks like making compounds with the heavier noble gases argon, krypton and xenon; possibly radon, but it doesn't seem like anyone would want to try that one because radon is radioactive.

Fluorine readily forms ionic fluoride salts, which contain the fluoride ion (F<sup>-</sup>), for example sodium fluoride (NaF). They are moderately toxic if ingested in sufficiently large quantities, but are otherwise as boring as regular ionic salts. Fluoride salts are used in [[water fluoridation]].

==Crazy cool facts==
[[File:Fluorine dioxide.svg|thumb|right|165px|<center>FOOF!</center>]]
*Elemental fluorine is a yellow gas that killed a lot of the people who tried to isolate it.
*Elemental fluorine is so reactive it can ''burn water''. 
*Fluorine is considered by most organic chemists to be the most annoyingly dangerous element to work with-- rightfully so, since it's so reactive that it oxidizes just about everything, and requires specialized equipment to store and work with.
*Fluorine, either free or as a fluoride ion in hydrofluoric acid, can dissolve ''glass'' – it is usually stored in flasks made of Teflon, which, by the way, is also made with fluorine.
*Hydrofluoric acid (HF) is corrosive, toxic and a contact poison, being much more dangerous than hydrochloric acid. If it gets into your blood, it will suck the [[calcium]] out of your bones into your bloodstream, screwing up your electrolyte balance, which can cause heart attack and death. People rarely encounter it, however, unless they're, e.g., involved with semiconductor manufacturing.
*Then there is the nasty darling of mad scientists everywhere, chlorine trifluoride. Three atoms of fluorine will combine with a single atom of chlorine (chlorine trifluoride, ClF<sub>3</sub>) to demonstrate emphatically that there are things more entertainingly hazardous than fluorine gas.<ref>[http://blogs.sciencemag.org/pipeline/archives/2008/02/26/sand_wont_save_you_this_time Things I Won't Work With: Sand Won't Save You This Time]</ref><ref>[http://blogs.sciencemag.org/pipeline/archives/2013/04/05/chlorine_trifluoride_some_empirical_findings Things I Won't Work With: Chlorine Trifluoride: Some Empirical Findings] ClF<sub>3</sub> versus other matter</ref> Does a whole frozen chicken usually catch fire spontaneously? Yes - if doused in chlorine trifluoride. It'd be an excellent oxidizer for rocketry, except for the fact that it sets everything on fire - including things like [[aluminum]] plate, people, water, concrete and sand. Of course, it wasn't oxidizing enough so Chlorine trifluoride oxide, chlorine trifluoride dioxide and chlorine pentafluoride were invented. 
*To top the one above, there is dioxygen difluoride, O<sub>2</sub>F<sub>2</sub> or more evocatively FOOF,<ref>For more horrifying details, visit http://what-if.xkcd.com/40/.</ref><ref>[http://blogs.sciencemag.org/pipeline/archives/2010/02/23/things_i_wont_work_with_dioxygen_difluoride Things I Won't Work With: Dioxygen Difluoride]</ref> an apt description of its reaction with any combustible material.
*The strongest known acid, hexafluorostibic acid (HSbF<sub>6</sub>) is more than one quadrillion times (that is nine zeroes following a 1) times as acidic as pure sulfuric acid. It is so acidic that it can force very strong acids to absorb a proton. Needless to say, this is an extremely corrosive material that can disintegrate almost anything other than Teflon. (Helium hydride is stronger)  

==Fluorine and conspiracy nuts==
Fluorine, in the form of [[salt]]s such as sodium fluoride, is an essential component in [[water fluoridation]], which some [[conspiracy theory|conspiracy theorists]] say is a plot to poison us all. In pharmaceuticals, organofluorines are used because they're ''less'' reactive. But, the same nutters nevertheless bring them up, for example fluoxetine - which contains no free fluoride.

==External links==
*[http://www.theodoregray.com/PeriodicTable/Elements/009/index.s7.html Theodore Gray's Periodic Table Table entry on fluorine] (including one of the scariest samples in his awesome collection, a quartz vial of fluorine gas)

==References==
{{reflist}}

[[Category:Elements]]
[[Category:Water fluoridation]]

Categories: Elements, Water fluoridation