Lewis Acid

[Gargi Patel 1F]

In class we used the example of BF3 being a Lewis acid, but why is that so? Why does BF3 want to accept an electron pair?

[Haley Kaneshiro 1F]

Hi! BF3 wants to gain an electron pair because Boron is an incomplete octet. This means that there are only 6 electrons in comparison to the complete 8 electrons in its valence shell. The deficiency in the electrons makes Boron Trifluoride eager to accept two more electrons to complete the octet. Hope this helped!

[wudisc2C]

Boron can have an octet, but it doesn't have to. So it can exist as BF3 or BF4-

In general a good rule to think about in Lewis Acids and Bases:

Lone pair acceptor = Lewis acid

Lone pair donor = Lewis base