Here's how to determine the oxidation state of manganese in potassium manganate (K₂MnO₄):

1. Know the Charges of Common Ions

* Potassium (K): +1

* Oxygen (O): -2

2. Set up an Equation

Let "x" represent the oxidation state of manganese (Mn). Since potassium manganate is a neutral compound, the sum of the oxidation states must equal zero:

2(+1) + x + 4(-2) = 0

3. Solve for x

* 2 + x - 8 = 0

* x - 6 = 0

* x = +6

Therefore, the oxidation state of manganese in potassium manganate (K₂MnO₄) is +6.