how to identify lewis acids

[Giovanni Anguiano-Gutierrez 3L]

I get confused when trying to identify lewis acids. I know that the acid accepts electrons and the base donates electrons, but then I get confused because I don't know how it's actually working? if that makes sense? For bronsted, I feel like it's much simpler.

[Kaylee Sepulveda 4G]

Hopefully this example will help:

The boron atom in boron trifluoride, BF3, only has six valence electrons. Since it does not have a complete octet, BF3 is a Lewis acid and reacts with many Lewis bases. In this case, a fluoride ion acts as the Lewis base and donates one of its lone pairs.

[Giovanni Anguiano-Gutierrez 3L]

This makes more sense! Does a lewis acid always have an incomplete octet?

[kendal mccarthy]

A lewis acid is anything that is able to take in a lone electron pair. Usually it has a positive charge or can be a expanded octet.