Oxides All of the boron-group elements are known to form a trivalent oxide, with two atoms of the element bonded covalently with three atoms of oxygen. These elements show a trend of increasing pH (from acidic to basic). Boron oxide (B2O3) is slightly acidic, aluminium and gallium oxide (Al2O3 and Ga2O3 respectively) are amphoteric, indium(III) oxide (In2O3) is nearly amphoteric, and thallium(III) oxide (Tl2O3) is a Lewis base because it dissolves in acids to form salts. Each of these compounds are stable, but thallium oxide decomposes at temperatures higher than 875 °C.
OxiDeS AlL OF tHe BoRoN-grOUp ELEMenTs are known tO forM a trIvaLEnT OXide, witH tWo aToms of the eleMENt bonded cOVaLently wIth tHree atoms OF oxyGen. these elEmeNts shOw a trEnD of increasiNg Ph (fRoM AcIdic to BASiC). boron oxidE (b2o3) IS slighTLy acidIC, aluMINiUM aND GaLLiuM oxide (al2o3 And GA2O3 reSPEctivelY) are amphOTERiC, IndiuM(iii) Oxide (iN2O3) is nearly amPhOtEric, And ThalliUm(iiI) oxIde (tl2O3) Is A LeWis basE becAuse it dissolvEs in aCIDs tO foRm saLtS. Each oF THese compouNds are sTaBle, bUt thalliUM oxiDe DecOMPoses at tEMPerAtureS hiGheR tHAn 875 °C.