Answer:
2-
Explanation:
The dichromate ion is the part of the compound that looks like: Cr2O7.
Our current compound is Ag2CrO7. The “2” on Ag indicates that there are two atoms of Ag in this compound, while the absence of a number on Cr2O7 indicates that there is only one atom of Cr2O7.
In order to maintain balance within the compound, the product of one of the ion’s charge with its atom amount must be equivalent to the product of the other ion’s charge with its atom amount. This is because the charges will ultimately add up to 0, which is the neutral substance we want.
Here, we know the “atom amount” of Ag is 2 and that its charge is 1+. So that’s 2 * 1 = 2. We also know that the “atom amount” of Cr2O7 is 1 and that its charge is x, for example. Then: x * 1 + 2 = 0. That means x = -2.
Thus, the charge on the dichromate ion is 2-.
