Which of the following is a cation?

• A. Na^+
• B. SO_4^{2-}
• C. Cl^-
• D. O^{2-}

Answer: (A)

Verified step by step guidance

1. Understand that a cation is a positively charged ion, meaning it has lost one or more electrons and carries a positive charge.
2. Look at each ion's charge notation: \(\mathrm{Na^+}\) has a positive charge, \(\mathrm{SO_4^{2-}}\) has a negative charge, \(\mathrm{Cl^-}\) has a negative charge, and \(\mathrm{O^{2-}}\) has a negative charge.
3. Identify which ion has a positive charge by focusing on the superscript indicating the charge sign and magnitude.
4. Recognize that \(\mathrm{Na^+}\) is the only ion with a positive charge, making it a cation.
5. Conclude that \(\mathrm{Na^+}\) is the cation among the given options because it carries a positive charge.