Germanium monoxide, GeO, is a chemical compound of germanium

Germanium

Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....

 and oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

. It can be prepared as a yellow sublimate at 1000°C by reacting GeO₂

Germanium dioxide

Germanium dioxide, also called germanium oxide and germania, is an inorganic compound, an oxide of germanium. Its chemical formula is GeO2. Other names include germanic acid, G-15, and ACC10380...

 with Ge metal. The yellow sublimate turns brown on heating at 650°C.. GeO is not well characterised. It is amphoteric dissolving in acids to form germanium(II) salts and in alkali to form "trihydroxogermanates" or "germanites" containing the Ge(OH)₃⁻ ion.