Question

What is the oxidation number of underlined element in each case $M{g}_2{\underset{–}{P}}_2{O}_7$?

(Write the absolute value of an answer)

Answer 1

Let $x$ be the oxidation number of $P$ in $M{g}_2{\underset{–}{P}}_2{O}_7$.
Since the overall charge on the compound is $0$, the sum of oxidation states of all elements in it should be equal to $0$.
Therefore, $2(2+)+2x+7(2-)=0$
Hence, $x=+5$.
Thus, the oxidation number of $P$ in $M{g}_2{\underset{–}{P}}_2{O}_7$ is $+5$.