GCSE›AQA GCSE Physics›Mind mapsThe Atom and Atomic ModelsAQA GCSE Physics: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsStructureTiny, positive nucleus of protons and neutronsNegative electrons surround the nucleusNucleus radius under 1/10 000 of atom radiusElectrons = protons, so no overall chargeEnergy levelsElectrons sit at fixed energy levelsAbsorb radiation → move up a levelMove down a level → radiation emittedNumbers, isotopesAtomic number = number of protonsMass number = protons + neutronsIsotopes: same protons, different neutronsCarbon-14 has 8 neutrons, carbon-12 has 6Lose outer electrons → positive ionThe atomand atomic modelspneModel timelineIndivisible sphere: no internal structurePlum pudding: positive ball with electrons embeddedNuclear model: from alpha scatteringBohr: electrons at fixed distancesCurrent: protons and neutrons in nucleusScattering evidenceMost alpha particles passed straight through gold foilA few were deflected backwardsMass and charge in a small dense nucleusThis disproved plum puddingExam tipsPlum pudding has no nucleusCharge concentrated in nucleus, not spread out