Which of the following is an anion?

• A. Na^+
• B. K^+
• C. Cl^-
• D. Mg^{2+}

Answer: (C)

Verified step by step guidance

1. Understand that anions are negatively charged ions, meaning they have gained one or more electrons.
2. Look at each ion's charge: Na^+ has a positive charge, so it is a cation, not an anion.
3. K^+ also has a positive charge, so it is a cation as well.
4. Cl^- has a negative charge, indicating it has gained an electron and is therefore an anion.
5. Mg^{2+} has a positive charge of +2, making it a cation, not an anion.