Here's how to write the skeleton equation for the reaction of phosphorus and oxygen:

Reactants:

* Solid phosphorus: P (s)

* Oxygen gas: O₂ (g)

Product:

* Diphosphorus pentoxide: P₂O₅ (s)

Skeleton Equation:

P (s) + O₂ (g) → P₂O₅ (s)