Chapter 6: Electronic Structure of AtomsChapter 6: Electronic Structure of AtomsConcept CheckReview: Light Behaves Like a Wave, or Does it?Practice ProblemAtomic Structure 1: Electron EjectionAtomic Structure 2: Line Spectra of AtomsThe Bohr Model of the H Atom (1913)The Bohr Model of the H Atom (1913) Predicts Line Spectra (Only for H)The Bohr Model of the H Atom (1913) Predicts Electron Ejection EnergyPractice ProblemPractice ProblemWave Nature of MatterConsequences of the Wave Nature of Electrons in AtomsOrbitals and Quantum NumbersQuantum Numbers are like Train Tickets…Practice ProblemWhat Should You Know?What Should You Know?Chapter 6: Electronic Structure of AtomsCH110 FA11 SAS 1Prepare for Recitation September 1stALEKS Prep Assignment due August 26thALEKS Objective 1 due August 30thANGEL Quiz 1, September 1stLecture 1: August 22nd(Course Introduction)Lecture 2: August 24thLecture 3: August 26thLecture 4: August 29thRead: Ch. 1; Ch. 2.1 – 2.4; Ch. 5.1 – 5.3; Ch. 6.1 – 6.6Additional Preparation*: BLB 1: 17; Packet 1: 1-5BLB 2: 4,31; Packet 2: 1,2,3BLB 5: 3,25,28;BLB 6: 4,25,27; Packet 6: 1-5*ALEKS work is necessary but not sufficient for exam level preparation! Do not neglect the packet!Reminder: Add/Drop period ends Wednesday, August 31stChapter 6: Electronic Structure of AtomsCH110 FA11 SAS 2By the end of Lecture 6 you should know:wavelength and frequency of light, dual nature of light, electronic transitions and line spectraBohr modelMatter acts as wavesHeisenberg Uncertainty PrincipleElectronic transitions of orbitalsQuantum numbers (n, , m, ms)Orbitals: their shapes and energiesOrbitals and atoms with many electronsSpin quantum number (ms): Pauli Exclusion Principle and Hunds RuleElectron Configurations using the periodic tableWhat is the structure of an atom?What are the properties of atoms?Remember: structure affects function!Where are the electrons located? What is the energy of an electron?KEY QUESTIONS: THE BIG PICTUREConcept CheckCH110 FA11 SAS 3Understanding electromagnetic energy led toquantum theory(it explains what we observe) which led toatomic structureand predictselectron configurationsand explainsperiodic trends of the elementsReview: Light Behaves Like a Wave, or Does it?CH110 FA11 SAS 4• Light and other electromagnetic radiationbehaves as a ______• Light and other electromagnetic radiation behaves as a ________ with kinetic energy• Light behaves like a particle with a wavelength. The particle is called a ______c = E = Speed of lightIn a vacuumKineticEnergyE =Practice ProblemCH110 FA11 SAS 5What is the total energy of one mole of green photons (wavelength equal to 523 nm)?A. 3.80 x 10-19kJ B. 6.32 x 10-43kJ C. 2.29 x 105kJD. 229 kJE. 632 kJ• Einstein’s Observation:• The energy of the light follows this rule:• NO e-will be emitted if ________Atomic Structure 1: Electron EjectionCH110 FA11 SAS 6Light in Electrons outmetalAlbert Einstein 1921 Nobel Prize in PhysicsObservation: Electrons are emitted by metal only if light has frequency greater than certain minimum value.Ek= KE of emittedphotoelectronAlbert Einstein: The Photoelectric Effect.direct observation of quantum effects!CH110 FA11 SAS 7Atomic Structure 2:Line Spectra of AtomsE3E2E1excited states ground state EnergyWhat if hν isn’t enough to eject an e-?• Absorption: energy of photon causes energy of electron to ________• Emission: giving off a photon causes energy of electron to ________•Observation:• Conclusion:The Bohr Model of the H Atom (1913)CH110 FA11 SAS 8Note: Orbit energy in the Bohr model is negative, so it must correspond to energy needed to put electron into the orbit.Neils Bohr, 1922 Nobel Prize in Physics, really, not such a bad guyTwo Postulates:1.Energy levels are quantized2. Transitions are quantized:n = 1, 2, ...RH Rydberg constant= 2.180 x 10–18Jn = principal quantum #Allowed Energy Levels: “Orbits”En = -RH(1/n2)The Bohr Model of the H Atom (1913)Predicts Line Spectra (Only for H)CH110 FA11 SAS 9n = 4n = 1n = 2n = 3etc. . . .Transitions are accompanied by absorption or emission of light:∆E = Efinal– EinitialRHni2If nf> nithen ∆E is + If nf< nithen ∆E is ––= 1nf21∆E =hνPredicts the H-atom spectrum EXACTLYThe Bohr Model of the H Atom (1913)Predicts Electron Ejection EnergyCH110 FA11 SAS 10n=1n=2n=3n=∞n = 1n = 2n = 3n = 4E/RH= E/RH= E/RH= E/RH= ∆E = hν = RHni2–1nf21Coulomb’s Law:n = ∞E/RH=Practice ProblemCH110 FA11 SAS 11Which of the following transitions in an H atom results in the emission of the highest energy photon?1. n=1 → n = 62. n=6 → n = 33. n=3 → n = 64. n=1 → n = 45. n=6 → n = 1Practice ProblemCH110 FA11 SAS 12For the H atom, what is the wavelength of light emitted for the ni= 2 → nf= 1 electronic transition?1. 574 nm2. 472 nm3. 219 nm4. 122 nm5. 101 nmWave Nature of MatterCH110 FA11 SAS 13Wave properties λν = cParticle properties E = hνDual nature of light:de Broglie (1924) asked the following:If light has a duality, why not matter too ?λ =hm·vm·v is ___________Because λ ∝ 1/m the effects are onlyobservable for extremely _____ masses• De Broglie wavelength• Wave properties of electrons areconfirmed experimentally:Electron microscopeThe Bohr model explained some experimental data for the hydrogen atom, but it failed for other atoms…Consequences of the Wave Nature of Electrons in AtomsCH110 FA11 SAS 14Electrons have wave properties:• The mass of the electron is well known• Spectroscopy results demonstrate that we can always measure an electron’s energy• Heisenberg Uncertainty Principle:• Can only calculate the _________ of locating of an electron in a volumeNot Orbits, but OrbitalsErwin Schrödinger, 1933 Nobel Prize in PhysicsWerner Heisenberg, 1932 Nobel Prize in PhysicsOrbitals and Quantum NumbersCH110 FA11 SAS 15Overview:1. Principal quantum number n=2. Azimuthal quantum number =3. Magnetic quantum number m=4. Spin quantum number ms =Bohr againQuantum Numbers are like Train Tickets…CH110 FA11 SAS 16Figure from Moore, Stanitski, Jurs (2005) Chemistry: The Molecular Science; Thomson Brooks/ColePractice ProblemCH110 FA11 SAS 17Which of the following is not a valid set of quantum numbers?1. n=4, = 3, m= 02. n=3, = 0, m= 13. n=4, = 1, m= 04. n=4, = 0, m= 05. All four sets obey the rulesWhat Should You Know?CH110 FA11 SAS 18Properties of Electromagnetic Radiation:1. What is spectroscopy? A continuous spectrum? A line
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