IB›IB Chemistry HL›Mind mapsS2.1 The ionic modelIB Chemistry HL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsForming ionsMetals lose electrons → cationsNon-metals gain electrons → anionsAim for a noble-gas configurationGroup 1: 1+; group 2: 2+; group 13: 3+Group 15: 3−; group 16: 2−; group 17: 1−Roman numeral gives charge: iron(III) = FeX3+\ce{Fe^3+}FeX3+Ionic bondElectrostatic attraction between opposite ionsActs throughout a 3D latticeIn NaCl each Na⁺ has six Cl⁻Written as empirical formulas, e.g. NaClStronger with higher charge, smaller radiusFormulas and namesBalance charges: MgX3NX2\ce{Mg3N2}MgX3NX2Binary compounds end -ide-ate means the ion contains oxygenAmmonium NHX4X+\ce{NH4+}NHX4X+, carbonate COX3X2−\ce{CO3^2-}COX3X2−Sulfate SOX4X2−\ce{SO4^2-}SOX4X2−, phosphate POX4X3−\ce{PO4^3-}POX4X3−Use brackets: CaX3(POX4)X2\ce{Ca3(PO4)2}CaX3(POX4)X2Ionic modelions and latticesNa⁺Cl⁻NaClMelting and volatilityHigh melting points, low volatilityMany strong attractions must be overcomeMgO 2852 °C, NaCl 801 °CConductivity, solubilitySolids do not conduct, ions are fixedMolten or aqueous: ions move and conductSoluble in polar solvents like waterInsoluble in non-polar hexaneAl₂O₃ and CaCO₃ insoluble: lattice too strongExam tipsIonic bonding is not sharing electronsIt is not a bond between just two ionsIons, not electrons, carry the chargeCalcium sulfide CaS; calcium sulfate CaSO₄