GCSE›Edexcel GCSE Physics›Mind mapsAtomic StructureEdexcel GCSE Physics: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsParts of an atomTiny positive nucleus of protons and neutronsNegative electrons surround the nucleusNucleus holds almost all the massAtom diameter is about 10−10 m10^{-10}\,\text{m}10−10mNeutral atom: protons = electronsParticlesProton: mass 1, charge +1Neutron: mass 1, charge 0Electron: mass ~11836\frac{1}{1836}18361, charge −1Positron: same mass as electron, charge +1IsotopesAtomic number = number of protonsMass number = protons + neutronsIsotopes: same protons, different neutronsCarbon-12 has 6 neutrons, carbon-14 has 8Atomic structureinside the atompneElectrons and ionsElectrons sit in set energy levelsAbsorb radiation → move to a higher orbitDrop to lower orbit → emit radiationLose outer electrons → positive ionModel historyPlum pudding: positive ball with embedded electronsRutherford scattering: alphas fired at gold foilBohr: electrons in fixed orbitsExam tipsMost alphas straight through → mostly empty spaceSome deflect or bounce back → small dense positive nucleusLink each observation to its conclusion