What do you call a negatively charged ion?

A negatively charged ion is referred to as an anion. This terminology comes from the behavior of the ion during electrolysis, where anions migrate towards the anode, which is the positive electrode. When an atom gains one or more electrons, it results in an overall negative charge due to the increased number of negatively charged electrons compared to positively charged protons in the nucleus.

In contrast, a cation is a positively charged ion, formed when an atom loses electrons. Protons and electrons themselves are subatomic particles that carry positive and negative charges, respectively, but they are not terms that describe ions. Therefore, calling a negatively charged ion an anion is the most accurate terminology in the context of chemistry.