Which of the following formulas represents the peroxide ion?

• A. O_3^{2-}
• B. O^{2-}
• C. O_2^{-}
• D. O_2^{2-}

Answer: (D)

Verified step by step guidance

1. Understand that the peroxide ion is a polyatomic ion consisting of two oxygen atoms bonded together with an overall charge of 2-.
2. Recall that the peroxide ion has the formula where two oxygen atoms are connected, and the total charge on the ion is 2-, which means the charge is distributed over the two oxygen atoms.
3. Analyze each given formula: \(O_3^{2-}\) represents a triatomic oxygen ion with a 2- charge, which is not peroxide; \(O^{2-}\) is a single oxygen ion with a 2- charge, known as oxide ion; \(O_2^{-}\) is a diatomic oxygen ion with a single negative charge, called superoxide.
4. Identify that the peroxide ion must have two oxygen atoms and a 2- charge, which corresponds to the formula \(O_2^{2-}\).
5. Conclude that the correct formula for the peroxide ion is \(O_2^{2-}\) because it matches the definition of two oxygen atoms bonded together with a 2- charge.