What is the formula for permanganate ion?

The permanganate ion is a polyatomic ion consisting of one manganese atom and four oxygen atoms. Its chemical formula is represented as ( \text{MnO}_4^{-} ), indicating that it carries a charge of -1.

In the case of the permanganate ion, the manganese is in a +7 oxidation state, and the four oxygen atoms are in the -2 oxidation state overall, which collectively account for the -1 charge of the ion. This makes it a strong oxidizing agent commonly used in various chemical reactions and applications, particularly in analytical chemistry.

The other formulas listed do not correspond to the correct oxidation state or charge of the permanganate ion. The option with the -2 charge does not reflect the accurate charge and would suggest a different ion altogether. Similarly, the options with +2 charge or three oxygen atoms fail to represent the composition and charge of the permanganate ion correctly. Thus, the correct formula for the permanganate ion is indeed ( \text{MnO}_4^{-} ).