How do we know something is a lewis acid or base?

[Henri_de_Guzman_3L]

I don't remember!

[bonnie_schmitz_1F]

A lewis acid is the electron acceptor and the lewis base is the electron donor!

[Stephen Sirmay 1I]

Bases donate pairs of electrons and acids accept pairs of electrons. A Lewis acid is therefore any substance, such as the H+ ion, that can accept a pair of nonbonding electrons. In other words, a Lewis acid is an electron-pair acceptor. A Lewis base is any substance, such as the OH- ion, that can donate a pair of nonbonding electrons. A Lewis base is therefore an electron-pair donor.The Lewis theory suggests that acids react with bases to share a pair of electrons, with no change in the oxidation numbers of any atoms. Many chemical reactions can be sorted into one or the other of these classes. Either electrons are transferred from one atom to another, or the atoms come together to share a pair of electrons.

[anthony_trieu2L]

It is helpful to draw the Lewis structure of the molecule when determining whether something is a Lewis base or acid. For example, if there is a lone pair on a central atom in a molecule, the molecule is mostly likely a Lewis base because it can donate those electrons to an acid.

[daniela3D]

Lewis Acid: takes a pair of electrons from another atom
*reasoning 1.) has an incomplete octet 2.) has a double/triple bond
Lewis Base: gives off a pair of electrons to another atom
*can donate to another lone pair