Which statement best describes an ion?

• A. An atom that has gained or lost electrons
• B. A neutral atom with equal numbers of protons and electrons
• C. A nucleus containing protons and neutrons
• D. A charged atom due to changes in nucleons

Answer: (C)

Ion is an atom with a net electric charge because electrons have been gained or lost. In a neutral atom, the number of protons is equal to the number of electrons, so the overall charge is zero. If electrons are removed, the atom becomes positively charged; if electrons are gained, it becomes negatively charged. The nucleus, consisting of protons and neutrons, defines the atom’s identity and mass, but it doesn’t determine whether the atom is ionized. A description involving changes in nucleons would imply altering the nucleus and the element itself, not just forming ions. So the best description is an atom that has gained or lost electrons.