Question

what is the oxidation state of phosphorus in NaH2PO2?

Answer 1

Let oxidation state (os) of P is NaH₂PO₂ be x
os of oxygen is -2
os of Na is +1
os of hydrogen is +1

Total os of a molecule is zero (if neautral).

So by adding os we get
(+1)+(+1X2)+(x)+(-2X2)=0
Or x=+1

So oxidation state of phosphorus in NaH₂PO₂ is +1.