Let us assume that **K is +1** and **O is -2** and then we calculate the **oxidation state of sulfur. **

We know that, the sum of the oxidation numbers must be zero for a compound. Now evaluating it, we get

**K**_{2}S_{2}O_{8}

2(+1) + 2x + 8(-2) = 0

2x = 14

x = +7 .... but, Sulfur doesn't exhibit an oxidation state of +7.

This is commonly called **sodium persulfate** and two of the oxygen atoms, like the **peroxide**, are in the -1 oxidation state

Now, For simplicity we will write the formula as

K_{2}S_{2}(O_{2})O_{6}

2(+1) + 2x + 2(-1) + 6(-2)

**x = +6 .... which is a viable oxidation state for Sulfur** **(S)**