The correct name of the ionic compound V₂O₅ is Vanadium V oxide, which is also often referred to as Vanadium pentoxide. In this compound, vanadium has an oxidation state of +5, hence the Roman numeral V.
The formula V₂O₅ indicates that there are two vanadium ions combined with five oxide ions. The naming convention for transition metals typically includes the oxidation state in Roman numerals after the name of the metal. Here, because vanadium is in a +5 state in V₂O₅, it is designated as ‘Vanadium V’.
This nomenclature helps to clarify which ionic species is present, especially since vanadium can exhibit multiple oxidation states, including +2 and +4.