Determining Lewis Acids and Bases

[Joanna Huang]

Can someone explain how to determine whether a molecule is a Lewis acid or base? In the sapling they talked about molecule structures and stuff in the answer, and I don't think we've gone over that yet... I know that a Lewis acid is an acceptor, but how do you know if it's an acceptor or now?

[TrishaP_3E]

One thing I look at is that if the molecule has a lone pair, it is probably going to be a donator (so a base).

When looking at a reaction like Cl-+ AlCl3 --> AlCl4-, Cl- would be the base because it is the ion that's electrons are used to form the fourth bond with AlCl3 to make it AlCl4-.

Hope this helped!

[Isabella Chou 1A]

To add on, molecules that have electron-deficient central atoms (for example, BeCl2) accept electrons and are thus Lewis acids.

[Jaclyn Schwartz 1I]

I usually look at charge or position on the periodic table of the element or ion. The most basic definitions are a lewis acid is an electron pair acceptor and a lewis base is an electron pair donor. As said above, lone pairs usually indicate donors. Acids usually needs electrons is another hint as well.

[Jordan_OBrien_2k]

The way that I remember which is the Lewis Acid is that the acid always aaccepts the electrons (they both start with A), and then obviously the base would have to donate the electrons.

[Eve Gross-Sable 1B]

You know that it is an electron acceptor if it needs to take on an electron to fill the shell. So this would be figured out by counting the valence electrons and then seeing what shell of the orbital that is and how many electrons it would have if it were full

[Jack_Pearce_2H]

Hey there!

For me, I like to first notice if there are any positive or negative net charges on the molecules. If they are negative, they are lewis bases and positive as lewis acids. If there are no net charges, I like to draw out the lewis structures and see if there are any unpaired electrons or atoms with incomplete octets. If there are incomplete octets, then they are acids, lone pairs, bases. eventually you'll get the hang of just looking at them and seeing which is which. Hope this helps!

[Heidi Buri 2I]

Hi! Lewis acids accept pairs of electrons while lewis bases donate pairs of electrons. In order to know if a substance is an acceptor or not, you have to look at how the act in a relation. In reactions, acceptors act as oxidizing agents (gains electrons in a relation).

[Jiapeng Han 1C]

If a species has an empty orbital, then it is a Lewis acid since it can accept lone pairs. If a species has lone pairs of electrons, then it is a Lewis base since it could donate electrons.

[Kyle Dizon 3A]

Lewis acids are often electron acceptors because they need the electron from lone pairs to satisfy the valence electrons that they need. From how I see it, lewis base are those who can afford donating or sharing the lone pairs around the orbitals that they have.