Which statement best describes ions?

• A. Atoms with extra neutrons
• B. Atoms with a magnetic field
• C. Atoms that have gained or lost electrons
• D. Atoms with equal numbers of protons and neutrons

Answer: (C)

Ions are atoms with a net electric charge because they have gained or lost electrons. The number of protons in the nucleus gives the identity and positive charge, while electrons balance that charge. When an atom loses electrons, it becomes positively charged; when it gains electrons, it becomes negatively charged. That change in electron count is what makes it an ion.

The other statements miss this key idea: extra neutrons would simply create a different isotope, not an ion. A magnetic field isn’t what defines an ion. And having equal numbers of protons and neutrons describes a particular nucleus, not the charged state of the atom.