In K2CrO7, the total charge of the compound must be zero since it is neutral. We know that potassium (K) has a fixed oxidation state of +1 in compounds, so the total oxidation state contributed by the potassium atoms is +2 (since there are two K atoms).
To determine the oxidation state of chromium (Cr), we can use the following formula:
Total charge = Sum of oxidation states of each atom
Since K2CrO7 is neutral, the total charge is zero. We can substitute the oxidation state of potassium (+2) and the total number of potassium atoms (2) into the formula:
0 = 2(+1) + x + 7(-2)
Simplifying, we get:
0 = 2 - 14 + x
0 = x - 12
Therefore, the oxidation state of chromium in K2CrO7 is +6.