What do we call an ion that has a negative charge?

An ion that has a negative charge is specifically referred to as an anion. This term is derived from the Greek word "anions," which means "to go up." In the context of chemistry, anions are formed when an atom or a molecule gains one or more electrons, resulting in a net negative charge due to the increased number of negatively charged electrons compared to positively charged protons.

In contrast to anions, cations are positively charged ions that result from the loss of electrons. A neutral atom has an equal number of protons and electrons, leading to no net charge, while a positron is the antiparticle of an electron and carries a positive charge, but is not considered an ion. Hence, the correct term describing a negatively charged ion is anion, as it directly captures the essential characteristic of having an excess of negatively charged electrons.