What is the common name for P2O3?

The compound P2O3 is commonly referred to as diphosphorus trioxide because its name is derived from the quantity and type of elements it contains. The prefix "di-" indicates the presence of two phosphorus atoms, while "trio-" signifies that there are three oxygen atoms in the molecular formula.

In systematic nomenclature, this naming approach is standard for molecular compounds formed between nonmetals, where prefixes are used to denote the number of atoms of each element. Consequently, the name “diphosphorus trioxide” accurately reflects the composition of the molecule, indicating specifically that there are two phosphorus atoms combined with three oxygen atoms.

The other options do not reflect the appropriate combination of phosphorus and oxygen atoms indicated by the molecular formula. Tetraphosphorus trioxide would imply the presence of four phosphorus atoms, phosphorus trioxide suggests there is only one phosphorus atom present, and phosphorus pentoxide indicates five oxygen atoms, which does not align with the actual formula of P2O3. Thus, diphosphorus trioxide is the correct and accepted common name for this compound.