Popular in General Chemistry
Popular in Chemistry
This 12 page Class Notes was uploaded by Chantellioh on Saturday October 10, 2015. The Class Notes belongs to Chem 142 at University of Washington taught by Xiaosong Li in Summer 2015. Since its upload, it has received 34 views. For similar materials see General Chemistry in Chemistry at University of Washington.
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Date Created: 10/10/15
Monday October 5 2015 Chemistry Notes Week 2 Day 1 Quantum Mechanics and Atomic Theory Just some General Information We are skipping differential equations using less math Quantum mechanics created by postulates didn t include math until it was better understood Chapter 12 Quantum Mechanics and Atomic Theory ENERGY defined in terms of relative magnitude Sources include sunlight wind waves Sunlight as energy source harvesting is not difficult but 2 problems arise storage no good method to store solar energy How to use it efficiently developing energy efficient materials 2 types of energy used in chemistry Potential energy PE mgh energy of object due to placement in force such as gravity Kinetic Energy KE 12mv2 energy of object due to motion m mass a accel due to gravity h height v velocity Chemical internal energy Chem internal energy KE and PE of molecules total energy in system Kinetic energy stems from translation motion through space rotation motion around center vibration motion directed through chemical bodies motion also relates to heat of the molecule Molecular potential energy stems from electrostatic bodies and Monday October 5 2015 chemical bodies Force field for this potential energy is the interaction btwn and charges Exo vs Endo thermic Exo results in loss of heat to environment 39 ex 2H20 gt 2H202 reactant s energy begins high eve gt process causes in a change in energy Ioss gt product relatively low in energy change is often referred to as A delta energy referred to as E Endo heat transfers TO chemical system reactant s energy begins low eve gt process causes change in energy gain gt product relatively high in energy QUANTUM MECHANICS Schrodinger one of founding fathers of Quantum mechanics QM cat experiment in cat put somewhere unseen it can either dead or alive and therefore is both dead and alive same logic used in QM for humans Also any object can be present in two places at one time when w QM Sneak peak into later lecture light does not have mass electrons have mass both are quantized Electromagnetic Radiation EMR Gamma and Xrays great energy source bc high frequency makes high energy but bad bc harmful bc A and other reasons we mostly use visible light and infrared radiation Mustshould know but likely won t be on exam EMR wave shape oscillating electric field perpendicular to oscillating magnetic field Maxwell s four partial differential equations Monday October 5 2015 Intensity of light proportional to absolute value of E2 Light is EMR wavelength from 400700 nm violet red nm 109 m nano almost atomic level 1010m 39 mm Characterized through wavelength A lambda distance btwn 2 successive peaks or troughs reguency v nu waves that pass a given point per second proves that waves travel unit cycles per second sec sec1 Hertz relationship between wavelength and frequency c Av 0 speed of light 30 x 108 ms All light ways have SAME SPEED speed of light can also be manipulated to Aclv or vcA Characteristics of Waves characterized by propagation of light LISTEN TO RECORDINGS Diffraction of Iigm pattern of LIGHT when shined through slit light and dark bands pattern of the WAVES called interference looks like wifi symbols w edges overlapping pattern of light when shine through crystal scattered the light parts are constructive interference add together to gain intensity the dark parts are destructive interference cancel each other out also applies to slit light and dark bands The Photoelectric Effect metals emit electrons when exposed to light Monday October 5 2015 Professor s Demonstration Used fur and plastic to generate electrons between aluminum aluminum repulsed separated used IR long A lights nothing happened used UV light aluminum reverted back to orign position discharged electrons gone bc light made metal emit its electrons Einstein s Experiment directed 700nm radiation metal surface used special electron detector to count ejected prediction electrons will be emitted bc energy of wave related to amplitude as long as high enough amp there will be electron ejection Prediction wrong 700 nm no electrons were emitted proved that light was quantized min frequency not amplitude required to eject electrons for any metal proved light s particles wave energy related to amp but light s related to freq Electrons only emitted certain shorter wavelengths Higher freq shorter wavelength ejects higher velocity electrons ejected proportional to strength intensity of light increasing intensity only increase electrons ejected NOT velocity of ejections PE Effect Equation KE hUphoton39CD h constant hv photon energy D Workfunction 39 Workfunctionhao minimum energy needed to release electrons needing to pay penalty to leave metal plate like work contract if light posses payment energy electrons leave if not such as w IR electrons must stay Monday October 5 2015 higher frequency more energy Wednesday October 7 2015 Chemistry Notes Week 2 Day 2 Quantum Mechanics and Atomic Theory Continued Chapter 12 Day 2 PROTONS AND ENERGY Relationship btwn Nu and Photon Energy Ephoton h6 but only valid for light h 6626 x 1034 Js a frequency E can be written in terms of light frequency energy can be released as light ex sun s released energy s in form of light imagine loss of PE such as when falling as release of light MUST BE ABLE TO FIND ENERGY OF A PHOTON GIVEN IT S WAVELENGTH OR FREQ FOR EXAM Steps to find energy given its wavelength x 1 List all known variables and relevant equations Known Variables Equations h 6626 X 103934JS Eph0t0n my 0 29979 x 108ms simplified to 300 x 108 CzMU gt azcl gt A 00 wavelength A X quotchoose which equation is most relative to your problem 2 Plug in what you can into each equation Ephoton hu gt Ephoton 6626 x 1034 0 0 CIA gt a 300 x108x 3 Use combination to create one equation from two Ephoton 6626 X 1034 300 X 108 X End Equation 4 Solve using calculator and reduce to the correct sig fig Can memorize End equations for reference but must know process and steps to get there Wednesday October 7 2015 bc interference experiment we know photon moves like wave bc energy exchange quantized Einstein says its a particle also only givestakes ALL energy not just a portion Photon s motion classifies as wave Photon s quantum properties classifies as particle WAVE PARTICLE DUALITY 39 REPETITION TO MAKE SURE YOU UNDERSTAND Light is a WAVE looks like a wave does NOT look like this a o 39 39o One wave is one photon the wave is the photon it s only a proton bc quantized energy change ENERGY QUANTIZATION Black Body Radiation BBB Experiment Thermite reaction used by Walter White in Breaking Bad to steal methyl amine So much heat in object radiates as photons light BBR Energy can convert from form of heat to light used by Planck to measure energy emitted but failed decided change in E must be quantized in terms photon energy ho 39 I AEhon n integer 1234 n photons emittedabsorbed for energy ho hplank s constant gt identical to Einstein s constant A discovery led to revolution in quantum mechanics Quantum Emission and Absorbance atoms emit and absorb energy some discrete wavelengths energy emitted is quantized if no quantums in energy colors would not exist only certain frequency of light absorbed by molecules gt colors Quantum model of Hydrogen Model by Bohr electrons circle nucleus in certain orbits orbit energies quantized described as En2178 x 1018J22n2l 2 atomic number protons in molecule n integer purely empirical not mathematical Wednesday October 7 2015 only works for elements w 1 electron in outermost level conventional for EO and n infinite bc no interaction btwn electrons and nucleus Friday October 9 2015 Chemistry Notes Week 2 Day 3 Quantum Mechanics and Atomic Theory Continued Chapter 12 Day 3 BOHR S QUANTUM MODEL OF THE H ATOM can be used to predictA E A EEfinal39Einitial Or Ehu and Cu quot gt E hcA h 6626 X 103934 c300x108 Emission and Absorption En392178 x 1018J22n2 ground state n1 lowest level Higher energy in n2 than n1 going from 2 1 requires loss of energy emission 39 released in terms of 1 photon per ho energy lostAE going from n1 to n2 requires gain of energy absorption 3 Theories of Atomic emission Lynn Series AKA UV emission drop from higher level to n1 BalmerSeries Visible emission drop from higher to n2 Paschen Series Infrared emission drop from higher to n3 Friday October 9 2015 Failure of Bohr s Model Bohr s model failed Model would equate to no stable atoms assumed electron is particle by assumption that but it works for systems w one electron electron has definite orbit more accurate to see electron as wave wave properties lead to photon characteristics quantization QUANTIZED VS CONTINUOUS SPECTRA electron energy levels in atoms quantized atoms form molecules gt energy levels mix gt quantized molecular energy levels amnt energy levels increase further w more atomic interactionsatoms forming molecules many many atoms form molecules gt all their energy levels mix gt dense quantized molecular energy eve gt form a continuum Two atoms two energy levels millions of atoms millions of energy levels energy levels are extremely close together bc so many of them form a continuum rather than several separate levels like a bridge when each plank of wood one energy level FORMAL QUANTUM MECHANICS skipping ch 126 MUST memorize outcome of Schrodinger s equation Diffraction of Particles matter such as electrons also has wave particle duality matter anything w mass diffraction patterns generated by electrons proves electrons are also waves not just particles Electrons have mass PHOTONS DON T HAVE MASS Friday October 9 2015 de Broglie s equation worked with Schrodinger to create ONLY WORKS FOR PARTICLES OF MASS for protons use co Ahmv v velocity m mass A wavelength h 6 626x1034 i mass of electron 912X1031 Wave Mechanics like photons each electron one wave leach wave one electron standing wave characteristics motion of electron are specific to each electron when limited by potential Standing waves don t appear to be moving directionally as left right caused by interference btwn identical waves going in opposite directions identical waves can come from other waves or bounded medium bounded medium allows it to interfere w reflection wave have quantized motion only work certain wavelengths good example of standing vs traveling wave httpphysicsinfowavesstanding Probability amplitudes vs Probability density Wavefunction LlJ psi probability amplitude describes specific motions of standing waves that electron can have LlJ2 probability density shows where largest amount of particle in standing wave is The Schrodinger Equation H2LJELJ H KEPE LIJ has all properties of an electron H hamiltonian operator KE and PE operators corresponds to total energy in system Friday October 9 2015 operators well defined math term Schro s eqtn finds set of quantized energy levels and specific wave forms see second point of Wave Mechanics an electron can have Electron Functions in H atoms 39 Vr Zeer Ze charge of nucleus e charge of electron electron charge 160217646 X 1019 Coulombs Don t forget negative sign in front of equation
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