Which of the following species contains an atom in the +6 oxidation state?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → CrO2Cl2
The oxidation state x of the metal comes from charge balance: the oxidation states of all atoms add up to the charge of the species (O = −2; Cl, F and CN = −1 each).
\( \ce{MnO4^-} \): x + 4(−2) = −1, so x = +7.
\( \ce{[Cr(CN)6]^3-} \): x + 6(−1) = −3, so x = +3.
\( \ce{[NiF6]^2-} \): x + 6(−1) = −2, so x = +4.
\( \ce{CrO2Cl2} \): x + 2(−2) + 2(−1) = 0, so x = +6.
Only chromium in \( \ce{CrO2Cl2} \) is in the +6 oxidation state.