Which of the following ions has a charge of -2?

The sulfate ion is indeed a polyatomic ion that carries a charge of -2. Its chemical formula is SO₄²⁻, which indicates that it has four oxygen atoms bonded to a sulfur atom, and the overall charge is -2 due to the electron gain by the entire ion. This characteristic makes sulfate a common component in various chemical reactions, particularly in acid-base chemistry and environmental processes.

Understanding the charges of other ions is essential, as it helps in predicting chemical behavior. For instance, the nitrate ion (NO₃⁻) carries a charge of -1, the carbonate ion (CO₃²⁻) has a -2 charge, and the phosphate ion (PO₄³⁻) has a charge of -3. However, it is the sulfate ion that specifically has the charge of -2 as asked in the question. Hence, recognizing the charge of sulfate is crucial for various applications in chemical equilibria and titration calculations.