What is an ion?

An ion is defined as an atom or molecule that has a net electric charge arising from the loss or gain of one or more electrons. When an atom loses electrons, it becomes positively charged, referred to as a cation, while if it gains electrons, it becomes negatively charged, known as an anion. This phenomenon occurs because the balance between protons (positively charged) and electrons (negatively charged) is disrupted, leading to a net charge.

The other options do not accurately capture the full definition of an ion. For example, stating that an ion is only a positively charged atom ignores the existence of negatively charged ions. Similarly, limiting the definition to only molecules or atoms with a specific charge fails to encompass the broader classification of ions that can occur in both atomic and molecular forms. Finally, describing an atom as one with an equal number of protons and electrons indicates a neutral state, not the charged state that defines an ion. Therefore, the option that describes an ion as an atom or molecule with a net electric charge due to the loss or gain of electrons is the most accurate understanding of what an ion is.