IGCSE›Cambridge IGCSE Chemistry›Mind mapsFormulae, Functional Groups and TerminologyCambridge IGCSE Chemistry: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsFormula typesMolecular formula = actual atoms in one moleculeEmpirical formula = simplest whole number ratioMolecular is a whole number multiple of empiricalGlucose CX6HX12OX6\ce{C6H12O6}CX6HX12OX6 has empirical formula CHX2O\ce{CH2O}CHX2OEmpirical methodDivide mass by Ar to get molesDivide by the smallest number of molesMultiply up if ratios are not whole numbersC 36 g, H 6 g, O 32 g → CX3HX6OX2\ce{C3H6O2}CX3HX6OX2EquationsBalance using coefficients onlyNever change the subscriptsStates: (s), (l), (g), (aq)2 Mg(s)+OX2(g)→2 MgO(s)\ce{2Mg(s) + O2(g) -> 2MgO(s)}2Mg(s)+OX2(g)2MgO(s)Formulaegroups and terminologyCH₂O−OH−COOHIonic formulaeCriss-cross: swap charges to become subscriptsUse brackets for polyatomic ions above 1Ca(NOX3)X2\ce{Ca(NO3)2}Ca(NOX3)X2 from CaX2+\ce{Ca^2+}CaX2+ and NOX3X−\ce{NO3-}NOX3X−Check total charge is zeroNet ionic: remove spectator ionsAgX+(aq)+ClX−(aq)→AgCl(s)\ce{Ag+(aq) + Cl-(aq) -> AgCl(s)}AgX+(aq)+ClX−(aq)AgCl(s)Organic termsFunctional group decides chemical propertiesHomologous series differ by CHX2\ce{CH2}CHX2Saturated = only single C−C bondsUnsaturated = contains C=CIsomers: same molecular formula, different structureAlcohol −OH, acid −COOH, alkene C=CExam tipsInclude state symbols in symbol equationsLearn meth-, eth-, prop-, but- prefixesDivide by the smallest first, then multiply if needed