Molybdenum bronze

In chemistry, molybdenum bronze is a generic name for certain mixed oxides of molybdenum with the generic formula A
xMo
yO
z where A may be hydrogen, an alkali metal cation (such as Li, Na, K), and Tl. These compounds form deeply coloured plate-like crystals with a metallic sheen, hence their name. These bronzes derive their metallic character partially occupied 4d-bands. The oxidation state in K_0.28MoO₃ are K, O, and Mo. MoO₃ is an insulator, with an unfilled 4d band.