Which ion has a charge of -1?

The ion that has a charge of -1 is Chlorate. Chlorate is a polyatomic ion with the chemical formula ClO₃⁻, indicating that it carries a negative one charge. This characteristic is key when discussing ionic compounds and their properties, as it helps in understanding how ions interact in chemical reactions and form compounds.

To provide some context, while carbonate (which has a -2 charge, CO₃²⁻) and phosphate (which has a -3 charge, PO₄³⁻) are both negatively charged polyatomic ions, they carry different charges than chlorate. A cation, by definition, has a positive charge, which further confirms that chlorate is the only ion among the choices listed with a -1 charge.