An atom with an unequal number of electrons and protons is known as what?

An atom with an unequal number of electrons and protons is classified as an ion. In essence, ions are charged particles that arise when an atom either gains or loses electrons. If an atom has more electrons than protons, it becomes a negatively charged ion known as an anion. Conversely, if it has more protons than electrons, it becomes a positively charged ion known as a cation.

The distinction of ions comes from their charge status, which contrasts with neutral atoms that have an equal number of protons and electrons, rendering them electrically neutral. Molecules, on the other hand, are formed when two or more atoms bond together, and they are not necessarily charged. Thus, whenever there's a difference in counting the fundamental subatomic particles of an atom—specifically electrons and protons—the result is an ion, which is why the correct answer is ion.