What is the oxidation state of phosphorus in H_3PO_3 , Ca_3P_2 , Na_3PO_4 and POF_3

Explanation

Due to high electronegativity of O, the O-in `H_2 O` forms strong intermolecular H-bonds. As such, water exists as an associated molecule while other hydribes of Group 16 do not form H-bonding and hence exist has discrete moleucles. As a result, water shows unusual physical properties, i.e., high b.p., high thermal stability and weaker acidic character as compared to other hydrides of Group 16.