Final Answer:
The chemical formula that is incorrect among the given options is 4) diphosphorus pentoxide.
Explanation:
In chemistry, the naming conventions for compounds are based on the valency of elements involved. The correct formula for diphosphorus pentoxide should be P₂O₅. In this compound, the prefix "di-" indicates there are two phosphorus atoms, and "penta-" denotes five oxygen atoms. However, the given formula "diphosphorus pentoxide" implies the presence of a single phosphorus atom with multiple oxygen atoms, which contradicts the convention. The correct formula aligns with the chemical properties and valency of the elements involved, making P₂O₅ the accurate representation for diphosphorus pentoxide.
The prefix "di-" implies the presence of two phosphorus atoms, while "pent-" indicates five oxygen atoms. According to the chemical rules governing nomenclature, the numerical prefixes directly correspond to the number of atoms for each element in the compound. Phosphorus typically forms compounds with a valency of 3 or 5, while oxygen commonly exhibits a valency of 2. The correct formula, P₂O₅, balances the valencies of phosphorus and oxygen, ensuring the compound's stability and consistency with chemical principles.
The incorrectness of the formula "diphosphorus pentoxide" lies in its misrepresentation of the number of phosphorus atoms, suggesting a single phosphorus atom rather than the actual two phosphorus atoms in the compound. This highlights the importance of adhering to chemical nomenclature guidelines to accurately represent the composition of compounds based on their constituent elements and their respective valencies.