IB›IB Physics SL›Mind mapsE.1 Structure of the atomIB Physics SL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsRutherfordAlpha particles fired at thin gold foilMost passed straight through: mostly empty spaceA few deflected at large anglesTiny dense nucleus holds the charge and massReplaced the plum-pudding modelNotationZAX^{A}_{Z}\text{X}ZAX: A nucleon number, Z proton numberNeutrons: N=A−ZN = A - ZN=A−ZNeutral atom has Z electronsIsotopes: same Z, different AEnergy levelsElectron energies are discreteMove down: photon emittedMove up: exact photon absorbedΔE=hf=hcλ\Delta E = hf = \frac{hc}{\lambda}ΔE=hf=λhc1 eV=1.60×10−19 J1\,\text{eV} = 1.60 \times 10^{-19}\,\text{J}1eV=1.60×10−19JAtomstructure of the atomAAAZZZNNNeVSpectraEmission: bright lines on dark backgroundAbsorption: dark lines on continuous spectrumDark lines match the emission wavelengthsLines are evidence for discrete levelsAbsorption starts from the ground stateCompositionLine pattern is a fingerprint of an elementMatch to lab spectra to identify elementsStar's outer layers produce absorption linesExam tipsElectrons are 7300× lighter than alpha, not the causeConvert eV to J before using hc/λMissing lines do not prove element absent