Exam 2 Notes
Popular in HNRS: Principles of Chemistry I
verified elite notetaker
verified elite notetaker
verified elite notetaker
verified elite notetaker
verified elite notetaker
verified elite notetaker
Popular in Chemistry
This 61 page Bundle was uploaded by BladeBrown on Tuesday October 27, 2015. The Bundle belongs to 141 at Michigan State University taught by Dr. Pollock in Fall 2015. Since its upload, it has received 208 views. For similar materials see HNRS: Principles of Chemistry I in Chemistry at Michigan State University.
Reviews for Exam 2 Notes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 10/27/15
CEIVI 141 Academic Coaching Dr Brown Agenda The Particle Nature of Light Photoelectric Effect Line Spectra Bohr s Model of the Hydrogen Atom Electrons as Waves The de Broglie Wavelength Quantum Numbers Atomic Orbitals The Particle Nature of Light Prior to the early 1900s light was thought to be purely a wave phenomenon Its behavior was described by the electromagnetic theory which treated the electric and magnetic fields that constitute light as waves propagating through space However a number of observations brought this classical view into question including the emission of electrons from metal surfaces on which light shines photoelectric effect and the emission of light from electrically excited gas atoms line spectra Photoelectric Effect The photoelectric effect is the observation that many metals emit electrons when light shines upon them Classical electromagnetic theory attributed this effect to the transfer of energy from the light to an electron in the metal which resulted in the dislodgement of the electron If light were a wave increasing the intensity of light should increase the energy of electrons and dislodge the electrons The experimental results did not support the classical prediction Photoelectric Effect Light Evacuated chamber Light Metal A surface W Posmve terminal Current Emltted 7 meter electrons V oltage SOU I CC a b I t k Tuesday October 13 2015 Photoelectric Effect Experimental results showed that the light exhibited a threshold frequency below which no electrons were emitted from the metal regardless of the intensity of the light In other words increasing the intensity of the light did not change the threshold frequency How can this be If light were a wave increasing the intensity should increase the energy of the electrons Photons and Quantized Energy Einstein postulated that light must come in packets A packet of light is called a photon or a quantum of light Energy is transferred as a particle photon that has a defined energy energy of a single quantum E hv One photon ejects one electron If the photon does not have enough energy then no electron is ejected Photons and Quantized Energy What is the energy of a photon of frequency 40 x 1018 5 1 h 6626 x 1034 M 26 x 108J 26 x 10 15J 17 x 10 52J 60 X 1051J 009 Photons and Quantized Energy What is the energy of a photon of frequency 40 x 1018 5 1 h 6626 x 1034 M 26 x 108J 26 x 10 15J 17 x 10 52J 60 X 1051J 009 Photons and Quantized Energy What is the wavelength of a photon of energy 62 x 10 8 J c 30 x 108 ms h 6626 x 10 34 J05 32 x 10 34 m 32 x 1018 m 32 x 10 18 m 94 x 1025 m 009 Photons and Quantized Energy What is the wavelength of a photon of energy 62 x 10 8 J c 30 x 108 ms h 6626 x 10 34 J05 32 x 10 34 m 32 x 1018 m 32 x 10 18 m 94 x 1025 m POP Line Spectra Bohr used the ideas of Planck and Einstein to explain the line spectrum of the hydrogen atom A spectrum is produced when radiation is separated into its component wavelengths A continuous spectrum consists of a continuous range of colors A line spectrum consists of individual discrete lines at specific wavelengths Continuous Spectrum Increasing wavelength Slits to isolate thin beam Line Spectrum Gas discharge tube contains hydrogen Bohr s Model of the Hydrogen Atom To explain the line spectrum of hydrogen Bohr assumed that electrons move in circular orbits around the nucleus Only orbits of certain radii corresponding to specific energies are permitted for the electron in a hydrogen atom Thus the energies of electrons in atoms are quantized Energy is emitted or absorbed by the electron only as the electron changes from one allowed energy state to another This energy is emittedabsorbed as a photon that has an energy E hv Bohr s model explained emission and absorption spectra by invoking discrete energy levels characterized by the quantum number n Bohr s Model of the Hydrogen Atom The lowest energy state n 0 nltgtc 1 is called the ground state A Z E gtExc1ted states O When the electron IS In a E C n 2 2 Transition from n 2 higherenergy state n 2 or i 100 M Jim iAElt6 gtlt Lphoton is emitted higher that atom is said to 55 3 JTransition from n I be in an eXCIted state m Ltonf 2 AE gt o 200 photon is absorbed 218 v n 1 Ground state Bohr s Model of the Hydrogen Atom o How much energy is required to L I Hydmgen move an electron from n 1 to NZ EVE Imizatimr a L 1000 n 2 levels n23 39 451 1 electron volt eV 16 x 10 19J 1112 34U A 136 eV B 34 eV C 102 eV D 151 eV quot n 1 Grunt Eta3911ea 4381 Energy Levele fr the Hydregen Mem Bohr s Model of the Hydrogen Atom o How much energy is required to L I Hydmgen move an electron from n 1 to NZ EVE Imizatimr a L 1000 n 2 levels n23 39 451 1 electron volt eV 16 x 10 19J 1112 34U A 136 eV B 34 eV C 102 eV D 151 eV quot n 1 Grunt Eta3911ea 4381 Energy Levele fr the Hydregen Mem The de Broglie Wavelength Louis de Broglie suggested that an electron moving about the nucleus of an atom behaves like a wave and therefore has a wavelength He proposed that the wavelength of the electron or of any particle depends on its mass and its velocity The de Broglie Wavelength Because de Broglie s hypothesis is applicable to all matter any object would give rise to a matter wave However the equation indicates that the wavelength associated with an object on the macroscopic level is so tiny that it is completely unobservable The de Broglie Wavelength What is the wavelength of an electron moving at 265 x 106 ms Mass of an electron is 91gtlt1O 3l kg h 6626 x 10 34 J05 1J 1 kgmzS 2 275 X 10quotl0 m 275 X 10 10J 193 x 103 m 193 x 103J 0090 The de Broglie Wavelength What is the wavelength of an electron moving at 265 x 106 ms Mass of an electron is 91gtlt1O 3l kg h 6626 x 10 34 Js 1J 1 kgmzs 2 275 x 10 l0 m similar to the size of an atom 275 X 10 10J 193 x 103 m 193 x 103J 0090 The de Broglie Wavelength What is the wavelength of Usain Bolt who can run 100 m in less than 10 s Let s say he has a mass of 100 kg h 6626 X 10 34 J05 1J 1 kgmzs 2 6626 X 10 34 m 6626 X 10 35 m 6626 X 10 37 m 6626 X 10 38 m 009 The de Broglie Wavelength What is the wavelength of Usain Bolt who can run 100 m in less than 10 s Let s say he has a mass of 100 kg h 6626 X 10 34 J05 1J 1 kgmzs 2 6626 X 10 34 m 6626 X 10 35 m 6626 x 10 37 m negligible basically meaningless 6626 x 10 38 m 009 The Uncertainty Principle The German physicist Werner Heisenberg proposed that the dual nature of matter places a fundamental limitation on how precisely we can know both the location and the momentum of an object at a given instant Heisenberg s Uncertainty Principle states that it is impossible to know simultaneously both the exact momentum of the electron and its exact location in space In other words we cannot simultaneously observe both the wave nature and particle nature of the electron QuantumMechanical Model of the Atom Schrodinger by treating electrons as waves derived by mathematical descriptions of the energies and probabilities of electrons The equation is called a wave equation and the description of an electron is called a wave function LIJ The probability of finding an electron is LUZ We use equations derived from quantum mechanics to describe both the energy of an electron and the probability of finding that electron in a region of space Quantum Numbers We call these regions of high probability for finding electrons atomic orbitals Each orbital can be described by a set of quantum numbers that are derived from quantum mechanical calculations There are four quantum numbers n principle quantum number describes the energy level of the orbital l angular momentum quantum number describes the shape of the orbital ml magnetic quantum number describes the orientation of the orbital ms spin quantum number describes the orientation of the spin of the electron Quantum Numbers The quantum number n can be a whole number integer starting with n 1 The quantum number I ranges from O to n 1 The quantum number ml ranges from l to l The quantum number ms can be either 12 or 12 Quantum Numbers If n 3 which of the following values for is NOT allowed A 0 B 1 C 2 D 3 Quantum Numbers If n 3 which of the following values for is NOT allowed A 0 B 1 C 2 D 3 Quantum Numbers If n 1 what are the allowed values for ml A ml O B ml 1 O 1 C ml 2 10 1 2 D ml 3 2 1 O 1 2 3 Quantum Numbers If n 1 what are the allowed values for ml A ml O B ml 1 O 1 C ml 2 10 1 2 D ml 3 2 1 O 1 2 3 Summary We can think of quantum numbers as a set of descriptors form electrons in an atom The position and energies of electrons in atoms can be described by atomic orbitals Each atomic orbital can contain a maximum of 2 electrons Understanding the idea that electrons can be described by orbitals of different shapes and specific energies allows us to understand how elements bond and react and the arrangement of the periodic table Atomic Orbitals 15 orbital surface J Tuesday October 13 2015 34 px orbital 39 Atomic Orbitals p orbital l quot 1v 4 d 7 4 Tuesday October 13 2015 pz orbital I 7 4 41 35 Atomic Orbitals Z Z Z 61x2 y2 orbital j y 1 a 2 x Tuesday October 13 2015 36 CEIVI 141 Academic Coaching Dr Brown Agenda Stoichiometry Limiting Reactants Percent Yield Recitation Sheet The Wave Nature of Light Electromagnetic Radiation Characteristics of Waves Properties of Waves Limiting Reactants A chemical reaction stops when any reactant is totally consumed leaving the excess reactants as leftovers The reactant that is completely consumed in a reaction is called the limiting reactant The limiting reactant determines or limits the amount of product formed The other reactant is called the excess reactant Calculate the amount of product possible from each reactant Whichever reactant yields the least amount of product is the limiting reactant Limiting Reagents The equation for a reaction is 2 S 3 02 gt 2 503 Consider a mixture of S and 02 GO in a closed container as illustrated below Which is the limiting reactant A B C D There is no limiting reactant s 02 so3 I I I 0000 CDCD I CD Limiting Reagents The equation for a reaction is 2 S 3 02 gt 2 503 Consider a mixture of S and O2 00 in a closed container as illustrated to the right Which of the following represents the product mixture 83 83 IIEII 080 5083 000000 083083 8350 000000 c8380 09 a b c Limiting Reagents The amount of product calculated when all of the limiting reactant is consumed is called the theoretical yield The amount of product actually obtained is called the actual yield actual yield Percent Yield x 100 theoretical yield Limiting Reagents Methyl tertbutyl ether MTBE C5H120 a substance used as an octane booster in gasoline can be made by reacting isobutylene C4H8 with methanol CH4O What is the percent yield of the reaction if 328 g of MTBE is obtained from reaction of 263 g of isobutylene with sufficient methanol C4H8 CH4O gt cSleo 1molCH 1molCHO 882gCHO 2 4 8 5 12 5 12 1 6 3 g C4st 561 g C4H8 X 1 mol C4H8 X 1 mol c H 4 3 g CSHIZO 512 Actual Yield 328 g o o 1 o 1 0 Percent YIeld Theoretical Yield x 00 413 g x 00 79 4A The Behavior of Electrons We will now explore the behavior of electrons within the atom and how they determine the chemical and physical properties of elements For example why do helium atoms only interact by London Dispersion Forces and why do H atoms interact to form covalent bonds As we will see later the quantummechanical model of the atom explains the behavior of electrons Before we explore electrons we must first understand the properties of light The WaveParticle Duality of Light Certain properties of light are best described by thinking of it as a wave while other properties are best described by thinking of it as a particle We will first explore the properties of light and then turn our attention to electrons to see how they also display the same waveparticle duality Electromagnetic Radiation Light is electromagnetic radiation a type of energy embodied in oscillating electric and magnetic fields A magneticfield is a region of space where a magnetic particle experiences a force An electricfield is a region of space where an electrically charged particle experiences a force Electromagnetic Radiation Electromagnetic radiation can be described as a wave composed of oscillating mutually perpendicular electric and magnetic fields propagating through space These waves move at a constant speed of 300 x 108 ms also known as the speed of light Electric field Magnetic field component component Direction of travel Amplitude and Wavelength We can characterize a wave by its amplitude and its wavelength The amplitude is the vertical height of a crest or trough The wavelength A is the distance between adjacent crests or troughs lt Wavelength A gt m Amplitude and Wavelength Wavelength and amplitude are independent properties The wavelength of light determines its color The amplitude of light determines its intensity or brightness the greater the amplitude the greater the intensity Amplitude and Wavelength Different amplitudes diiferent brightness Different wavelengths di erent colors KA gt Tuesday October 6 2015 14 Frequency Light is also characterized by its frequency v the number of cycles or wave crests that pass through a stationary point in a given period of time Frequency is inversely proportional to the wavelength the farther apart the crests the fewer that will pass a fixed location per unit time Therefore we can write the equation Vz Frequency Kg 5 fo f T39fv 3 Kg squot f m w human u w w quotu Jquot Tuesday October 6 2015 stationary point W MM 16 Amplitude Wavelength and Frequency a b 1 Which one has a higher intensity 390 2 Which one has a higher frequency b 3 Which one has a longer wavelength 3 Wavelength and Frequency Determine the wavelength of an X ray with a frequency of 30 x 1018 Hz c 30 x 108 ms C V A 8 12330X10 MS21X1010m V 30x1018s 1 1x10 10mx 1m 1x10 1nm 1gtlt109 m The Electromagnetic Spectrum The electromagnetic spectrum includes all wavelengths of electromagnetic radiation Frequgncya I I I I I I I I I I I I I I I I I I I I I vliz 104 106 108 1039 10392 1014 10396 10l8 103 1022 1024 Visible light Low Radio Microwave Infrared ltraviolet Xray Gamma ray High ener ener 9quot AFEI TV FM Ci 9quot wavelength I I I I I I I F I I I I I I I I I I I I I A m 105 103 10 10 1 10quot3 10 5 10 7 10 9 10 ll 10quot3 10quot395 750 Red 700 650 600 550 Wavelength A nm 450 400 Violet Tuesday ctober 6 2015 19 The Electromagnetic Spectrum Which one has the longest wavelength C Which one has the highest frequency A Which one has the highest energy A A Xray B visible C infrared Frequency 1 I I I I I I I I I I I I I I I I I I I I I I HZ 10 10 10quot 10 1012 1039quot 1016 10quotquot 103 1032 103 Visible light Low Radio Microwave lnfrareckiltravnolet Xray Gamma ray High ener ener 5 A 1 TV Frill oil 9quot WiWClcngUquot I I I I I I I I I I I I I I I I I I I I I m 10S 103 10 10quot1 10 3 10 5 107 10 9 10 10quot 10 l5 750 700 650 600 550 500 450 400 Red Wavelength A nm Violet Interference Waves interact with each other in a characteristic way called interference If two waves of equal amplitude are in phase when they interact that is the align with overlapping crests a wave with twice the amplitude results This is called constructive interference If two waves are completely out of phase when they interact that is they align so that the crest from one source overlaps with the trough from the other source the waves cancel by destructive interference Interference Waves Constructive in phase interference Waves out V Destructive of phase N interference Tuesday October 6 2015 22 Diffraction Waves also exhibit a characteristic behavior called diffraction When a wave encounters a slit that is comparable in size to its wavelength it bends or diffracts around it Wave crests Wave 7 i Dif f ti l Diffracte WEIUE Barrier with Slit Interference Patterns The diffraction of light through two slits separated by a distance coupled with interference results in an interference pattern Whether the interference is constructive or destructive depends on the difference in the path lengths traveled by the waves The resulting interference pattern appears as a series of bright and dark lines on a screen Interference Patterns Interference from Two Slits Film Film Slits top view front View Waves out of phase make dark spot Destructive interference Path lengths differ by M2 Constructive interference I Equal path lengths Waves in phase make bright spot Light I Tuesday October 6 2015 25 Diffraction pattern
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'