The number of P-O-P bridges in the structure of P₄O₁₀ and P₄O₆ are respectively

Answer: 6 and 6

P₄O₁₀ (phosphorus pentoxide) has 10 oxygen atoms in total. In its molecular structure four oxygens are present as terminal =O (each bonded only to one P), so the remaining oxygen atoms are10−4=6. Those six oxygens each link two phosphorus atoms → they are six P–O–P bridges.

P₄O₆ (phosphorus trioxide) has 6 oxygen atoms and none are terminal =O. All six oxygens are shared between two phosphorus atoms, so all six act as P–O–P bridges.

So both molecules contain six P–O–P bridging oxygen atoms — hence the number of P–O–P bridges is 6 (in P₄O₁₀) and 6 (in P₄O₆).