Ion

An ion, in the discussion of tartar dissolution, is a molecule where the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge.

Since protons are positively charged and electrons are negatively charged, if there are more electrons than protons, the atom or molecule will be negatively charged. This is called an anion.

Conversely, if there are more protons than electrons, the atom or molecule will be positively charged. This is called a cation.