Determine the oxidation state of phosphorus in the compound ${\text{NaH}}_2{\text{PO}}_2$.

Solution

1. Assign oxidation states: $\text{Na}=+1$, $\text{H}=+1$, $\text{O}=-2$.
2. Let the oxidation state of $\text{P}$ be $x$.
3. The sum of oxidation states in a neutral molecule is zero: $1 + 2(1) + x + 2(-2) = 0$.
4. Solving the equation: $1 + 2 + x - 4 = 0$, which simplifies to $x-1=0$.
5. Thus, $x=+1$. Hence the answer is (A).