Which of the following correctly identifies the cation and anion present in the compound CrO2?

• A. Cr^{6+} (cation) and O^{2-} (anion)
• B. Cr^{3+} (cation) and O_2^{-} (anion)
• C. Cr^{2+} (cation) and O_2^{2-} (anion)
• D. Cr^{4+} (cation) and O^{2-} (anion)

Answer: (A)

Verified step by step guidance

1. Identify the chemical formula given: \(\mathrm{CrO_2}\). This compound contains chromium (Cr) and oxygen (O).
2. Recall that oxygen typically forms anions with a charge of \$2-\(, so each oxygen atom is \)\mathrm{O^{2-}}$.
3. Since there are two oxygen atoms, the total negative charge contributed by oxygen is \$2 \times (-2) = -4$.
4. To balance the overall charge of the compound (which is neutral), the chromium cation must have a charge of \(+4\) to offset the \(-4\) from oxygen.
5. Therefore, the cation is \(\mathrm{Cr^{4+}}\) and the anion is \(\mathrm{O^{2-}}\).