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What I know is, elements with octet are stable, But In BF3, Boran doesn't get octet, So, How come BF3 molecule exist? If it exists, How do we know whether it is BF3 or not? Is there any proof that shows BF3 exists?

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Boron trifluoride, as described in Wikipedia is proved to exist the way everything in chemistry is ultimately proved, by experiment. The octet rule is really only a model that describes the electronic structure of some but not all molecules. Boron trifluoride is one of those (many, actually) molecules for which the octet rule is not really correct. The actual electronic structure is not just a single Lewis structure but a combination of multiple contributing structures, some of which do satisfy the octet rule and some of which don't.

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  • $\begingroup$ The octet rule is not really a model either; it's a rationalisation of an observation. It's been shown for many compounds to work, and on that basis it was suggested it works for many more. Also the octet rule is an upper limit. $\endgroup$ Aug 25 '18 at 12:35
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Yes $\ce{BF_3}$ does exist. In fact its a Lewis acid . Since it doesn't have its octet complete it is called as hypovalent. Also there is Back bonding happening in $\ce{BF_3}$ as Fluorine has electrons to donate and Boron has empty orbital available and the back bonding is of the type $\ce{2Pπ-2Pπ}$ due to which there is partial double bond character and hence it helps in making boron less electrophilic thereby increasing its stability. Here are some properties of boron trifluoride -https://en.m.wikipedia.org/wiki/Boron_trifluoride

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  • $\begingroup$ What you said is theroetically possible, But where can I get real existence proof?, I mean, Can you show me the existence of BF3 not in theoretical way.??(like with photos, Composition of a Bf3 compound or anything but theory?) $\endgroup$
    – John Paul
    Aug 24 '18 at 17:31
  • $\begingroup$ Please see edited answer $\endgroup$
    – Pan
    Aug 24 '18 at 17:34
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    $\begingroup$ To make your answer better I'd add some of the known physical properties and synthetic routes. Maybe even references to commercial sources. Heck, you can buy it from chemical suppliers. $\endgroup$
    – matt_black
    Aug 25 '18 at 13:05
  • $\begingroup$ @Matt_black the OP exactly wants some proof of existance of Borontrifluoride so if you can then please add some proif in the answer $\endgroup$
    – Pan
    Aug 26 '18 at 4:56

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