Question

which is the correct formula for phosphorus pentachloride?
o pcl4 because a subscript of 4 indicates four cl atoms
o pcl5 because a subscript of 5 indicates five cl atoms
o p5cl because a subscript of 5 indicates five p atoms
o p5cl3 because a subscript of 5 indicates five p atoms

Explanation:

磷（P）的氯化物中，“pentachloride”表示有五个氯原子，在化学式中氯原子的数量用下标表示，所以五氯化磷的化学式是PCl₅。

Answer:

PCl₅ because a subscript of 5 indicates five Cl atoms