GCSE›AQA GCSE Chemistry›Mind mapsElectronic StructureAQA GCSE Chemistry: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsChanging modelSolid sphere came firstPlum pudding: electrons in positive ballNuclear model: tiny central nucleusBohr: electrons in fixed shellsParticlesProton: charge +1, mass 1Neutron: charge 0, mass 1Electron: charge −1, very small massAlmost all the mass is in the nucleusElectron structureinside the atomp+ne-2,8,1NumbersAtomic number = protonsMass number = protons + neutronsNeutrons = mass number − atomic numberNeutral atom: electrons = protonsIsotopesSame element, different number of neutronsChlorine-35: 17 protons, 18 neutronsChlorine-37: 17 protons, 20 neutronsShellsElectrons fill the lowest energy level firstShell maximum: 2, 8, 8Sodium is 2,8,1Alpha scattering: most pass through, few bounce back