What is the metal oxidation state in #"dichromate ion"#, #Cr_2O_7^(2-)#?

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Answer 1 · 2017-05-28T08:33:59

In #"dichromate"#, #Cr_2O_7^(2-)#? We got #Cr(VI+)#.

The SUM of the individual oxidation states of chromium and the oxygen atoms in dichromate anion is equal to the charge on the ion.

And thus #2xxCr_"oxidation number"+7xxO_"oxidation number"=-2#.

Now oxygen generally has an oxidation of #-2# in its compounds, and it does so here, so.............

#2xxCr_"oxidation number"+7xx(-2)=-2#.

Add +14 to both sides..............

#2xxCr_"oxidation number"=+12#.

#Cr_"oxidation number"=+12/2=+VI#, as required................