Question

In calcium hypophosphite, oxidation number of phosphorus is

• A. $0$
• B. $+1$
• C. $+3$
• D. $+5$

Answer 1

Answer: (B)

$+1$

The charge on the hypophosphite, $H_{2}P{O}_2^{-}$ ion is $-1$ .
The oxidation numbers of H and O are $+1$ and $-2$ respectively.
Let $x$ be the oxidation number of phosphorus, then the sum of the oxidation numbers will be equal to $-1$, which is the charge on the ion. Hence, $2(+1)+x+2(-2)=-1$ or, $x=+1$. So, the oxidation state of phosphorus is +1.