What is the name for P_2O_5?
The name is diphosphorus pentoxide.Binary compounds with oxygen in them have oxide as a last name.The first name is phosphorus.We give the numbers of each atom:di (=2) phosphorus penta (=5) oxide, which means: 2 phosphorus together with 5 oxygenThe a of penta is omitted when it comes before o as in oxide. Often the di- is also omitted (as the other compound also starts with di-), and it is called just phosphorus pentoxide.Extra :An older name would be phosphoric oxide, %P_2O_5%, as opposed to phosphorous oxide %P_2O_3%, which is the other possibility.The systematic name for %P_2O_5% is phosphorus(V) oxide. The numeral V signifies the oxidation number of phosphorus, which is +5.In the same way %P_2O_3% is called phosphorus(III) oxide, as the oxidation number of phosphorus is +3.
%P_2O_5% is commonly named phosphorus pentoxide. An interesting fact about phosphorus pentoxide is that %P_2O_5% is actually its empirical formula; its molecular formula is actually %P_4O_10%. The compounds name however was derived from its empirical formula, not from its molecular formula. The standard name for this compound is actually diphosphorus pentoxide. The di- prefix is used to show that the compound contains two phosphorus atoms and the penta- prefix is used to show it contains five oxygen atoms.
Phosphorus pentoxide is the most used name for %P_4O_10%, the white molecular solid whose empirical formula is %P_2O_5%. It is the anhydride of phosphoric acid. This is the image of the molecule from wikipedia.
For its avidity of water, it is one of the most powerful known dehydrating agent.