What is the oxidation number of chromium in the dichromate polyatomic anion, Cr2O7^(2-)?
Answer and explanation
Correct answer: A. +6
- Step 1: Let oxidation state of Cr be x. Oxygen has state -2 in oxides. Step 2. 2x + 7(-2) = -2 => 2x - 14 = -2 => 2x = 12 => x = +6. Answer: +6. Why not the others: +3 is the reduced form (Cr3+ in acidic media); +7 is impossible for Group 6 transition metals.
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