What is the formula of the compound formed between phosphorus and oxygen in its highest oxidation state?
P (group 15, valence 5 in +5 state) forms P₂O₅ with oxygen (valence 2), a stable acidic oxide.
Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Electronic Configuration and Types of Elements - s p d f Blocks