How do you work out the oxidation number of an element in a compound? E.g finding the oxidation number of the element Cr from the compound Cr2O3

1 Answer
Jan 8, 2018

The overall compound has a no charge (neutral). That means the positive and negative charges are equal in number. For the compound Cr_2 O_3, Chromium is a metal and hence its oxidation number is positive, lets say +x is its oxidation number. The oxidation number of oxygen is already known i.e -2. So, we can write an equation, as

2* (+x) + 3* (-2) = 0
(We equate it to zero because he overall charge is 0)

or 2x-6 = 0

or 2x= +6

or x = +3