Gallium is found primarily in the +3 oxidation state. The +1 oxidation state is also found in some compounds, although it is less common than it is for gallium's heavier congeners indium and thallium. For example, the very stable GaCl2 contains both gallium(I) and gallium(III) and can be formulated as GaIGaIIICl4; in contrast, the monochloride is unstable above 0 °C, disproportionating into elemental gallium and gallium(III) chloride. Compounds containing Ga–Ga bonds are true gallium(II) compounds, such as GaS (which can be formulated as Ga24+(S2−)2) and the dioxan complex Ga2Cl4(C4H8O2)2.
gallIuM is FouNd priMARilY iN tHE +3 oxidAtion sTATe. THe +1 oXidATion state is also fouNd in soMe cOmPoUnds, aLthouGh it iS lesS commOn than it Is foR gaLlium'S hEavieR congeNers inDIum and THalLium. For ExamplE, the vERY stabLe gaCl2 contAInS bOTh GalliuM(i) anD Gallium(iII) and cAN bE FormulatEd As gaigaiiicL4; in CoNtrast, tHE monochLoRIDE Is unsTabLE above 0 °c, dispRoportIoNaTinG Into elEmEntaL GalliUm anD gallium(iii) chlorIDe. CoMpouNds contAining ga–gA bonDs are trUe GalLium(iI) compounds, sUCH aS gas (whicH caN be FormuLated as Ga24+(s2−)2) AnD The dioxan CoMpleX Ga2cl4(C4H8o2)2.