pentoxides

Pentoxides are a class of oxides in which the metal or central element is in the +5 oxidation state, producing typically five oxygen atoms per formula unit. The term covers both discrete molecular pentoxides, such as dinitrogen pentoxide (N2O5), and solid, polymeric oxides with the general M2O5 composition (M = vanadium, niobium, tantalum, arsenic, antimony, etc.). In common usage, pentoxide names often reflect the parent element’s chemistry as well as the empirical M2O5 formula or the specific molecular oxide.

Representative members include phosphorus pentoxide (P4O10, also described as P2O5) and its application as a powerful dehydrating agent, vanadium(V) oxide (V2O5), niobium(V) oxide (Nb2O5), tantalum(V) oxide (Ta2O5), and arsenic(Ⅴ) oxide (As2O5), among others. Dinitrogen pentoxide (N2O5) is a distinct molecular pentoxide that serves as a strong nitrating agent and a precursor in various nitrogen-oxide chemistry. The chemistry of pentoxides spans covalent network structures (as in P4O10, Nb2O5, Ta2O5) to molecular species (as in N2O5).

Structure and bonding vary among members. Many solid pentoxides form extended frameworks built from MO6 octahedra or related polyhedra, whereas P4O10 and related phosphorous oxides exist as discrete molecular units that hydrolyze to phosphoric acid. Dinitrogen pentoxide is a covalently bonded molecular oxide that decomposes to nitrogen dioxide and oxygen on heating.

Applications and properties reflect their acidity and oxidizing power: V2O5 and related oxides are catalysts for oxidation reactions; P2O5 acts as a drying agent and strong acid anhydride; N2O5 is used in nitration chemistry. Safety considerations arise from their dehydrating or oxidizing nature and potential explosive tendencies in some cases.