Manganate ion (MnO₄²⁻)

Manganate is one manganese atom bonded to four oxygen atoms, with a 2− charge. It has the same atoms as permanganate but one more electron, because its manganese is in the +6 state instead of +7: 6 − 8 = −2. Its salts are dark green, and potassium manganate is the step on the way from manganese dioxide to potassium permanganate in industry.

• Manganate and permanganate both have four oxygens, so here the prefix per- marks the higher oxidation state rather than an extra oxygen.
• Green manganate is stable only in strongly basic solution; in neutral or acidic water it splits into purple permanganate and brown manganese dioxide.
• In the “chemical chameleon” demonstration, purple permanganate turns green as it is reduced to potassium manganate, K₂MnO₄, in a basic solution.

Compounds that contain manganate

Other ions with a −2 charge