Cracking the SAT Chemistry Subject Test

Sometimes it happens that an atom loses or gains one or more electrons. When
that happens, the number of electrons outside the nucleus is not equal to the
number of protons inside. The atom isn’t electrically neutral anymore and has
become an ion. If the atom loses one or more electrons, it has fewer negative
charges than positive charges, so it is a positively charged ion, or cation. If the
atom gains one or more electrons, it has more negative charges than positive
charges. This is a negatively charged ion, or anion.