Identifying Acids and Bases

[Jasmine 2C]

Rather than memorizing strong acids and bases (and thus knowing which are weak acids and bases), is there a way to tell from the molecule's structure? Like lone pairs, charges, etc?

[Ryan 1K]

Yes, if a molecule has a lone pair, it could be used to bond with H+. By donating an electron to the H+, it acts as a Lewis base.

For charges, we know that positive transition metal cations act as acids by weakening the bond between H and O in H2O molecules. We also know that negatively charged anions will likely act as a base since they are more likely to donate electrons rather than accept them.

However, I would suggest memorizing the strong acids and bases because those are very important in determining the strength of their conjugates, which in turn, is used to determine the acid-base behavior of salts.

[Maggie Eberhardt - 2H]

If you want to calculate the dissociation constants of the acids/bases then I guess you wouldn't have to memorize which are the strong ones, but considering there are only about six strong acids and the bases follow the trend of groups 1 and 2 on the periodic table, memorization might make your life easier.
That being said, you can also look at the strength of bonds and conjugate base/acid stability in order to determine relative strength and possibly determine from that whether they completely dissociate or not.