Incomplete Octet

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Iona Pay
Posts: 43
Joined: Fri Sep 28, 2018 12:15 am

Incomplete Octet

Postby Iona Pay » Sun Nov 04, 2018 10:45 pm

Why is boron able to provide both electrons when bonding with fluorine, and be satisfied with an incomplete octet?

Sierra Cheslick 2B
Posts: 61
Joined: Fri Sep 28, 2018 12:27 am

Re: Incomplete Octet

Postby Sierra Cheslick 2B » Sun Nov 04, 2018 10:57 pm

Boron does not provide both electrons - one electron is from boron and one is from fluorine in each of the three bonds in BF3. Boron is satisfied with only 6 valence electrons because since it only has 3 valence electrons, it can only form a maximum of three bonds, unless there is another atom that is willing to provide both electrons for the bond. This happens in the ion BF4-.

danicatran4
Posts: 35
Joined: Fri Sep 28, 2018 12:17 am

Re: Incomplete Octet

Postby danicatran4 » Sun Nov 04, 2018 11:00 pm

How will you know if boron (or any other element) will be satisfied with an incomplete octet (BF3) or want a complete octet (BF4-)?

Sydney Tay 2B
Posts: 64
Joined: Fri Sep 28, 2018 12:20 am

Re: Incomplete Octet

Postby Sydney Tay 2B » Sun Nov 04, 2018 11:03 pm

BF4- undergoes a coordinate covalent bond which means that 2 electrons come from one atom which in this case would be the extra fluorine atom. The reason why in BF3 boron is stable with an incomplete octet is because fluorine has such a high ionization energy that it is unlikely to exist with a positive formal charge.

Atul Saha 3D
Posts: 30
Joined: Fri Sep 28, 2018 12:25 am

Re: Incomplete Octet

Postby Atul Saha 3D » Sun Nov 04, 2018 11:03 pm

This mostly requires memorization, as that specific group has these unique properties. Boron and Aluminum are the two most common elements that might show up on examinations.

Much Joy,
Atul

JiangJC Dis2K
Posts: 72
Joined: Fri Oct 12, 2018 12:16 am

Re: Incomplete Octet

Postby JiangJC Dis2K » Mon Nov 05, 2018 8:18 am

The four exceptions are hydrogen, lithium, beryllium, and boron. These are the first 5 elements on the periodic table, so you they have only 5,4,3,2, or 1 electrons to start with. Therefore they cannot form more bonds than valence electrons.


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