Chapter 7: Electronic StructureLightElectromagnetic RadiationLight as a WaveSlide 5Electromagnetic SpectrumSlide 7Proof of WavesSlide 9Slide 10Light as a ParticleSlide 12Slide 13Line SpectraSlide 15High Voltage ExcitationIdentifying MetalsSlide 18Bohr TheorySlide 20Slide 21Slide 22Matter as a WaveSlide 24Uncertainty PrincipleSlide 26Slide 27Slide 28Slide 29Slide 30Slide 31Quantum MechanicsHy = EyAtomic OrbitalsSlide 35Slide 36Slide 37Slide 38Slide 39Quantum NumbersSlide 41Slide 42Slide 43Slide 44Slide 45Subshell DesignationsOrbitalsSlide 48Slide 49Chapter 7: Electronic Chapter 7: Electronic StructureStructureElectrons in an atom determine virtually all of the behavior of the atom.Quantum theory – the study of how energy and matter interact on an atomic level.To understand the electron, we must first understand light.Reason =LightLightAlso known as electromagnetic radiation.Ex) Visible light, Infrared, X-ray, Radio.All electromagnetic radiation have several common characteristics.◦Light as a wave◦Light as a particle◦“Duality of Light”Electromagnetic RadiationElectromagnetic RadiationLight as a WaveLight as a WaveWavelength ( – lambda) = Frequency ( – nu) =Light as a WaveLight as a Wave•Wavelength and Frequency are inversely related.Electromagnetic SpectrumElectromagnetic SpectrumShows the full range of electromagnetic radiation that exists.Light as a WaveLight as a WaveThe product of the wavelength and the frequency, though, is a constant.c = , where c is the speed of light.Thus, if we know the frequency, we can find the wavelength and vice versa.LEP #1(a).Proof of WavesProof of WavesWaves exhibit certain properties when they interact with each other.Young’s Double Slit experiment.Proof of WavesProof of WavesProof of WavesProof of WavesLight as a ParticleLight as a ParticleThe wave nature of light does not explain all of the properties of light.Blackbody radiation – when solids are heated, they will glow.Color depends on the temperature.Light as a ParticleLight as a ParticleMax Planck – proposed a theory that energy from blackbody radiation could only come in discrete “chunks” or quanta.E = h h = 6.626 x 10-34 J-sLEP #1(b).Light as a ParticleLight as a ParticleThe photoelectric effect (Einstein) also is proof that light must have a tiny mass and thus act as a particle (photon).LEP #2, #3.Line SpectraLine SpectraWhen a gas like H2, Hg, or He is subjected to a high voltage, it produces a line spectrum consisting of specific wavelengths.Line SpectraLine SpectraHigh Voltage ExcitationHigh Voltage ExcitationIdentifying MetalsIdentifying Metals Na = yellow K = violet Li = red Ba = pale greenLine SpectraLine SpectraThe four lines for hydrogen were found to follow the formula:Where the values of n are integers with the final state being the smaller integer.( )72 2f i1 1 1 = 1.097 10 / m - λ n n� ��� �� �Bohr TheoryBohr TheoryHow could such a simple equation work?Niels Bohr some thirty years later came up with a theory.Classic physics would predict that an electron in a circular path should continuously lose energy until it spiraled into the nucleus.Bohr TheoryBohr Theory1. An electron can only have precise energies according to the formula: E = -RH / n2 ; n = 1, 2, 3, etc. and RH is the Rydberg constant.2. An electron can travel between energy states by absorbing or releasing a precise quantity of energy.Bohr TheoryBohr TheoryBohr TheoryBohr TheoryCan not explain the line spectra for other elements due to electron-electron interactions.Thus, the formula for Hydrogen can only be applied for that atom.LEP #4.Matter as a WaveMatter as a WaveLouis de Broglie proposed that if light could act as both a wave and a particle, then so could matter.Where h is Planck’s constant, m is the objects mass, and v is its velocity.Size, though, matters. LEP #5.hλ = mvMatter as a WaveMatter as a WaveDe Broglie was later proven correct when electrons were shown to have wave properties when they pass through a crystalline substance.Electron microscope picture of carbon nanotubes.Uncertainty PrincipleUncertainty PrincipleGerman scientist Werner Heisenberg proposed his Uncertainty Principle in 1927.HistoryUncertainty PrincipleUncertainty PrincipleFor a projectile like a bullet, classic physics has formulas to describe the motion – velocity and position – as it travels down range.Uncertainty PrincipleUncertainty PrincipleAny attempt to observe a single electron will fail.Uncertainty PrincipleUncertainty PrincipleIf you want to measure length, there is always some uncertainty in the measurement.To improve the certainty, you would make a better measuring device.Heisenberg, though, stated that the precision has limitations.x - mv h / 4Uncertainty PrincipleUncertainty PrincipleOnce again, size makes a big difference.LEP #6Uncertainty PrincipleUncertainty PrincipleDeterminacy vs. IndeterminacyAccording to classical physics, particles move in a path determined by the particle’s velocity, position, and forces acting on it◦determinacy = definite, predictable futureBecause we cannot know both the position and velocity of an electron, we cannot predict the path it will follow◦indeterminacy = indefinite future, can only predict probabilityUncertainty PrincipleUncertainty PrincipleQuantum MechanicsQuantum MechanicsThe quantum world is very different from the ordinary world.Millions of possible outcomes and all are possible!Quantum Café“I am convinced that He (God) does not play dice.” Albert EinsteinHH = E = EErwin Shrödinger proposed an equation that describes both the wave and particle behavior of an electron.The mathematical function, , describes the wave form of the electron. Ex) a sine wave.Squaring this function produces a probability function for our electron.Atomic OrbitalsAtomic OrbitalsA graph of 2 versus the radial distance from the nucleus yields an electron “orbital”.An “orbital” is a 3D shape of where an electron is most of the time.An “orbital” can hold a maximum of two electrons.Atomic OrbitalsAtomic OrbitalsThe Probability density function represents the probability of finding the electron.Atomic OrbitalsAtomic Orbitals•A radial distribution plot represents the total probability
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