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Unformatted text preview: QUANTUM THEORY AND MECHANICS MECHANICS
Chapter 5 What is light? What
♦ Properties of light? ♦ Particles and Waves ♦ Light waves = electromagnetic waves ♦ Electromagnetic radiation ♦ Wave Characteristics: – Amplitude – Wavelength – Frequency – Speed Electromagnetic Radiation Radiation
♦ Increases in penetration, frequency, energy ♦ Decreases in wavelength
Radio waves Microwaves IR Visible light Ultraviolet X-ray Gamma ROYGBIV Amplitude Amplitude
♦ The height of the wave measured from The the origin to its crest or peak. the ♦ Determines the brightness or intensity of Determines the light. the ♦ A measure of the maximum rise or fall of measure a wave. wave. ♦ Ψ = meters. Wavelength Wavelength
♦ The distance between successive crests of The the wave. the ♦ Includes one crest and one trough. ♦ Contains three consecutive nodes (crest Contains to crest or trough to trough). or ♦ λ = meters. Frequency Frequency
♦ Tells how fast a wave oscillates up and Tells down. down. ♦ Measured by the number of times a light Measured wave completes a cycle of upward and downward motion in one second. downward ♦ Repetitions or cycles per second. ♦ ν = 1/s = hertz = Hz. Velocity Velocity
♦ Light regardless of its wavelength moves Light at a constant speed. at ♦ Speed of light (c) = 3.00 x 108 m/s. ♦ Wavelength vs. Frequency: c=λxν or or λ=c/ν Quantum Theory Debate Quantum Wave Theory Rutherford-Bohr models of the atom starts the debate. ♦ Believe that the electron is only energy that Believe moves in the form of a wave. moves ♦ They set out to calculate the energy of each They orbit of Hydrogen from the work of Balmer. orbit ♦ Max Planck: “Planck’s Hypothesis”
– Proposed “quanta” or small packages of energy. E=hxν ♦ Believe that the electron is only a particle that Believe Particle Theory Particle has mass and travels in a straight line. has ♦ They set out to calculate the energy of each They electron in the Hydrogen atom. electron ♦ Albert Einstein: “Relativity” E = mc2 ♦ Louie DeBroglie Duality Theory Duality ♦ Electron is both a particle and wave Electron (matter waves). (matter Wavelength = Planck’s constant Wavelength Planck’s momentum Quantum Mechanical Atom Quantum
♦ Erwin Schrodinger. ♦ Electron exists in a cloud in regions of Electron energy requirement based upon 2πr = λ. energy ♦ The highest probability of finding the The electron is closest to the nucleus. ♦ Heisenburg Uncertainty Principle
– The position and momentum of a moving The object (electron) cannot be measured and known exactly. known Quantum Mechanics Quantum
♦ Electron density: the density of an Electron electron cloud. electron ♦ Atomic orbital: a region around the Atomic nucleus of an atom where an electron with a given energy is likely to be found. with ♦ Orbitals have characteristic shapes, sizes, Orbitals and energies. and ♦ S (spherical), p (dumbbell), d & f (more (spherical), complex). complex). Quantum Mechanics Quantum
♦ Principle energy level = n. ♦ The energy of the electron increases as n The increases. increases. ♦ Ground state vs excited state ♦ Sublevels: the number of sublevels in Sublevels: each principle level equals the quantum number (n). number
– s, p, d, f. – 1s, 2s, 2p, 3s, 3p, 3d, etc. Quantum Mechanics Quantum
♦ Orbitals: each sublevel consists of one or more Orbitals: orbitals. orbitals. ♦ Electron’s “address”: consists of the principle Electron’s energy level, the sublevel, and its orbital within that sublevel. that
♦ Electron spin: Electron – Clockwise (+ ½) or Counterclockwise (- ½). – Two electrons per orbital.
– Energy comparisons between sublevels / orbitals. – The number of orbitals increases by odd integers. Electron Configuration Electron
♦ The distribution of electrons among the The orbitals of an atom. orbitals ♦ Determined by distributing the atom’s Determined electrons among levels, sublevels, and orbitals based on a set of stated principles. principles.
♦ Ground state: Electrons populate the Ground – Based on the relative energy of the orbitals. lowest energy levels (most stable / can be predicted). predicted). Electron Configurations Configurations
♦Carbon 1s22s22p2 ♦Sample Problems Sample (pg. 135 #8-9) (pg. ♦Homework Problems. Predicting Configuration Predicting
♦ Figure 5-7 pg 133 ♦ Aufbau Principle: Electrons are added Aufbau one at a time to the lowest energy orbital available. available. ♦ Pauli Exclusion Principle: An orbital can Pauli hold a maximum of 2 electrons. hold ♦ Hund’s Rule: Electrons occupy equal Hund’s energy orbitals so that a maximum number of unpaired electrons result. number Orbital Diagrams Orbital
♦ Horizontal diagram depicting how electrons populate orbitals. electrons Carbon : 1s2 2s2 2p2 1s 2s 2p ...
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This note was uploaded on 01/28/2011 for the course CHEM 101 taught by Professor Petrovich during the Fall '08 term at N.C. State.
- Fall '08