An electron-ordering transition occurring in a mixed-valent system that results in an ordering of formal valence states in the low-temperature phase. Example: The prototype system, first identified by Verwey, is the ferrospinel magnetite, $\ce{Fe^{3+}[Fe^{3+}Fe^{2+}]O4}$ in which an ordering of $\ce{Fe^{3+}}$ and $\ce{Fe^{2+}}$ ions within octahedral sites is thought to occur below \(T_{\rm{v}}\approx 120\ \rm{K}\).