What defines ions?

Ions are defined as atoms that have gained or lost one or more electrons, resulting in a net positive or negative charge. When an atom loses electrons, it becomes positively charged, known as a cation. Conversely, when an atom gains electrons, it becomes negatively charged, known as an anion. Thus, the correct definition encompasses both positively charged and negatively charged atoms, which directly corresponds to the provided answer.

In this context, the other options do not accurately capture the definition of ions. The notion that ions can only form covalent bonds is misleading since ions primarily engage in ionic bonding, especially in the formation of compounds. Additionally, the claim that only negatively charged atoms are ions is incomplete, as it excludes positively charged ions. Lastly, stating that ions do not bond with anything overlooks their fundamental role in forming various chemical compounds, particularly ionic compounds. Therefore, the broad definition that encompasses both types of charged atoms is essential for understanding the nature of ions.