Which statement is true about ions relative to neutral atoms?

• A. Ions always have more protons than electrons.
• B. Ions have more neutrons than the corresponding neutral atom.
• C. Ions have the same number of protons but a different number of electrons.
• D. Ions have the same number of electrons as protons.

Answer: (C)

The number of protons sets which element you have; forming an ion changes only the electrons. When an atom loses or gains electrons, it keeps the same number of protons, but the electron count changes, creating a charged species. That’s why ions have the same number of protons as the neutral atom but a different number of electrons, leading to a positive charge if electrons are lost or a negative charge if electrons are gained. For example, a sodium atom becomes Na+ after losing an electron, while chlorine becomes Cl− after gaining one. Neutrons aren’t involved in ion formation, so they don’t have to differ from the neutral atom.