IB›IB Physics HL›Mind mapsE.1 Structure of the atomIB Physics HL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsRutherfordAlpha particles fired at thin gold foilMost pass straight through: empty spaceFew large deflections: tiny dense nucleusNuclide ZAX^{A}_{Z}\mathrm{X}ZAX: A nucleons, Z protonsNeutrons: N=A−ZN = A - ZN=A−ZEnergy levelsElectrons in discrete energy levelsDownward jump emits one photon: hf=ΔEhf = \Delta Ehf=ΔEEmission: bright linesAbsorption: dark lines, same wavelengthsLine pattern reveals compositionNuclear sizeR=R0A1/3R = R_0A^{1/3}R=R0A1/3, R0≈1.20×10−15 mR_0 \approx 1.20 \times 10^{-15}\,\text{m}R0≈1.20×10−15mVolume proportional to ADensity same for all nucleiρ≈2.3×1017 kg m−3\rho \approx 2.3 \times 10^{17}\,\text{kg m}^{-3}ρ≈2.3×1017kg m−3Atom structurenucleus to BohrAAAZZZeVClosest approachAll EkE_kEk becomes electric potential energyEk=k(2e)(Ze)dE_k = \frac{k(2e)(Ze)}{d}Ek=dk(2e)(Ze) gives dd is an upper limit on nuclear radiusHigh energy: strong force lowers large-angle scatteringBohr modelAngular momentum quantised: mvr=nh2πmvr = \frac{nh}{2\pi}mvr=2πnhEnergies: E=−13.6n2 eVE = -\frac{13.6}{n^2}\,\text{eV}E=−n213.6eVAllowed orbit: no radiationFails for atoms with several electronsExam tips1 eV=1.60×10−19 J1\,\text{eV} = 1.60 \times 10^{-19}\,\text{J}1eV=1.60×10−19J: convert firstDoubling A raises R by only 1.26Ionisation energy from n = 1: 13.6 eV