In chemistry, a zwitterion, formerly called a dipolar ion, is a molecule with two or more functional groups, of which at least one has a positive and one has a negative electrical charge and the net charge of the entire molecule is zero.

Because they contain at least one positive and one negative charge, zwitterions are also sometimes called inner salts. The charges on the different functional groups balance each other out, and the molecule as a whole is electrically neutral. The pH where this happens is known as the isoelectric point.

Unlike simple amphoteric compounds that may only form either a cationic or anionic species, a zwitterion simultaneously has both ionic states.

Amino acids are examples of zwitterions.

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