Chapter 7Two Branches of Mechanical Physics§7.2 Electromagnetic RadiationSlide 4If the frequency of a particular type of light is 8.57 x 1014 s-1, what is the wavelength of this light?§7.2 Interference§7.2 Diffraction§7.2 The Photoelectric EffectSlide 9§7.2 Einstein and the PE Effect§7.2 The Photoelectric Effect – a Summary§7.2 Quantum Mechanics§7.2 Photon Energy§7.3 Electron TransitionsPowerPoint PresentationSlide 16Slide 17Slide 18A Cumulative Problem§7.3 Evidence for Electron Transitions§7.3 Atomic Spectrum of Hydrogen§7.3 Line Spectra§7.3 Flame TestsSlide 24The Luminol ReactionChemiluminescence§7.4 Wave-Particle Duality§7.4 Electrons as Waves and Particles§7.4 The deBroglie EquationSlide 30§7.4 The Heisenberg Uncertainty Principle§7.5 Niels Bohr§7.5 The Bohr EquationSlide 34§7.5 Hydrogen Line SpectrumSlide 36What energy change occurs when an electron in the ground state is removed from He+ ion?Slide 39§7.5 The Bohr Model§7.5 The Quantum Mechanical Model§7.5 Quantum Numbers§7.5 Principal Quantum Number, nSlide 44§7.5 Angular Momentum Quantum Number (l)Slide 46§7.5 Forbidden Orbitals§7.6 Orbitals§7.6 Electron Density MapsSlide 50§7.6 s Orbitals (l = 0)§7.6 Nodes§7.6 Radial Distribution Functions§7.6 p Orbitals (l = 1)§7.6 Degenerate Orbitals§7.6 d Orbitals (l = 2)§7.6 f Orbitals (l = 3)§7.6 g Orbitals (l = 4)§7.5 Energy Shells and SubshellsTHE QUANTUM MECHANICAL MODELChapter 7Two Branches of Mechanical PhysicsClassical Mechanics – laws describing the motion of macroscopic objectsQuantum Mechanics – principles of electrical and magnetic properties at the atomic and subatomic level§7.2 Electromagnetic RadiationAll electromagnetic radiation travels in waves. Waves have three basic characteristics:1) Wavelength (λ) - the distance between the crests or troughs of a wave.2) Frequency (nu, ѵ) - the number of waves per second passing a certain point. 3) Speed (c) – all electromagnetic radiation has the same speed, the speed of light (c):c = 2.9979 × 108 m/s§7.2 Electromagnetic RadiationAll electromagnetic radiation travels at the speed of light.As wavelength decreases, frequency increases, and vice versa:λ↑ѵ↓ λ↓ѵ↑This reciprocal relationship is:λ ∙ ѵ = cUnits of  are in m; ѵ are s-1 (hertz).If the frequency of a particular type of light is 8.57 x 1014 s-1, what is the wavelength of this light?This light is actually ultraviolet and not in the visible range.§7.2 InterferenceWaves interact with each other via interference. Constructive interference – two waves add to make a larger waveDestructive interference – two waves cancel each other out§7.2 DiffractionDiffraction - waves (not particles) bend around an opening in a barrier.Diffraction through two slits gives an interference pattern of the diffracted waves.§7.2 The Photoelectric EffectPhotoelectric Effect - when exposed to certain light, metals eject electrons from their surface.← a metalThe PE requires a minimum or threshold frequency (0) of light (not intensity) to occur.Metals exposed to light at or above the threshold frequency emit electrons. §7.2 The Photoelectric Effect§7.2 Einstein and the PE EffectEinstein proposed electromagnetic radiation (EMR) is a stream of particles (photons).Ephoton ∝ Intense EMR dislodges more electrons, it has more photons than dim EMR.§7.2 The Photoelectric Effect – a Summary ≫ 0 > 0 < 0dim EMRfewer electrons ejected, higher velocityfewer electrons ejected, lower velocityno electrons ejectedbright EMRmore electrons ejected, higher velocitymore electrons ejected, higher velocityno electrons ejected0 = threshold frequency = frequency of EMR used§7.2 Quantum MechanicsPlanck’s constant (h) = 6.626 × 10-34 J ∙ sEnergy is quantized, it can only be released or absorbed in specific amounts called quanta (hѵ).This equation solves energy per particle.§7.2 Photon EnergyThis equation accounts for the energy of a photon itself or an electron transition.A photon is a quantity of energy so Ephoton must be positive.[photon = system][electron = system](+) only(+) or (–)§7.3 Electron TransitionsElectrons can absorb a photon and move to a higher energy level.Electrons in high energy states are unstable and lose energy as photons, dropping to lower energy states.e‒hh= photone‒ = electronabsorptionWhere is the photon?A photon is energy; theelectron absorbed it and used it to jump a quantum level.e‒ hh= photone‒ = electronemissionWhere is the photon?The electron released it (energy) when it fell to a lower-energy level.§7.2 Photon EnergyFor a HeNe laser with a wavelength of 632.8 nm, what is the energy associated with a photon and one mole of photons?= 1.890 × 105 J/mol==EphotonNumber ofphotonsWhat frequency of radiation is required to supply 1.0 × 102 J of energy from 8.5 × 1027 photons? §7.2 Photon EnergyA Cumulative ProblemHow many photons will be required to raise the temperature of 2.0 g water by 2.0 K if the water is exposed to infrared radiation of wavelength 2.8 × 10-4 cm? Cs(H2O) 4.18 J/g∙°C Ephoton = 7.1 x 10-20 J/photon= 16.7 JNumber of photons =7.1 × 10-20 J/photon16.7 J= 2.4 × 1020 photons§7.3 Evidence for Electron TransitionsAtoms - line spectraMolecules – chemiluminescence, fluorescence, phosphorescence§7.3 Atomic Spectrum of HydrogenContinuous spectrum(all visible colors)Line spectrum of H2(only a few lines)§7.3 Line SpectraUnique to each element Line spectra ≠ the continuous spectrum because electron energies are quantized.Each line corresponds to an electronic transition.§7.3 Flame TestsElements display various colors of light upon exposure to heat.The color is characteristic of the element and represents one or more strong lines in its line spectra.§7.3 Evidence for Electron TransitionsAtoms - line spectraMolecules – chemiluminescence, fluorescence, phosphorescenceThe Luminol ReactionLuminol + 2H2O2 Luminol* + 2H2O + O2 Luminol* + Sensitizer Luminol + Sensitizer*fluorescencechemiluminescencelightlightChemiluminescenceLuminol is used by CSI to locate traces of bodily fluids even after a crime scene has been cleaned. Iron and certain enzymes catalyze the luminol reaction.§7.4 Wave-Particle DualityAll matter exhibits both