Question

which of the following statements is true about ions?
anions form when an atom loses protons.
cations form when an atom loses electrons.
cations form when an atom gains electrons.
anions form when an atom gains protons.

Explanation:

• Anions are negatively - charged ions. They form when an atom gains electrons, not when it loses protons or gains protons. Protons are in the nucleus and are not easily lost or gained in ion - formation (except in nuclear reactions which are not relevant here).
• Cations are positively - charged ions. They form when an atom loses electrons. When an atom loses electrons, the number of protons (positive charge) is greater than the number of electrons (negative charge), resulting in a positive charge. If an atom gains electrons, it would form an anion (negative charge), not a cation.

Answer:

Cations form when an atom loses electrons.