Question
Assign oxidation number of the underlined elements in each of the following species:

Solution

Let the oxidation number of P = x
Writing the oxidation number of each atom at the top of its symbol.
+1 x - 2
H4 P2O7
Sum of the oxidation number of various atoms = 0
4(+1)+ 2x + 7(-2) = 0
i.e. x - 5 = 0
or x = +5
