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Download Chapter 4.2 Quantum Models
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Electrons in Atoms The Quantum Model of the Atom Quantum Model of Atoms Tuesday, September 11 Take out your Chapter 4 Vocabulary Terms and Periodic Table Take out one sheet of paper, title “ Quantum Model of Atoms” 1. What changes the amount of electrons ejected in the photoelectric effect? 2. What is a quantum? Quantum Model of Atoms Wednesday, September 12 Take out your “ Quantum Model of Atoms” notes from yesterday Copy and Answer: 1. What does n = 3 indicate? 2. What does l= 1 tell you about the atom? 3. What does the angular quantum number tell you? Photoelectric Effect Demo http://phet.colorado.edu/en/simulation/photoelectric The Quantum Model of the Atom Electrons as Waves French scientist Louis de Broglie suggested that electrons should be considered waves confined to the space around an atomic nucleus It followed that the electron waves could exist only at specific frequencies (energies) According to the relationship E = hν (Planks Law), these frequencies corresponded to specific energies—the quantized energies of Bohr’s orbits The Quantum Model of the Atom Electrons as Waves Electrons, like light waves, can be bent, or diffracted Diffraction refers to the bending of a wave as it passes by the edge of an object or through a small opening Electron beams, like waves, can interfere with each other Interference occurs when waves overlap Quick Lab Does light show the wave property of interference when a beam of light is projected through a pinhole onto a screen? Wave Interference The Quantum Model of the Atom The Heisenberg Uncertainty Principle German physicist Werner Heisenberg proposed that any attempt to locate a specific electron with a photon knocks the electron off its course The Heisenberg uncertainty principle states that it is impossible to determine simultaneously both the position and velocity of an electron or any other particle The Quantum Model of the Atom The Schrödinger Wave Equation In 1926, Austrian physicist Erwin Schrödinger developed an equation that treated electrons in atoms as waves laid the foundation for modern quantum theory Quantum theory describes mathematically the wave properties of electrons and other very small particles The Quantum Model of the Atom The Schrödinger Wave Equation Electrons do not travel around the nucleus in neat orbits, as Bohr had postulated Instead, they exist in certain regions called orbitals An orbital is a three-dimensional region around the nucleus that indicates the probable location of an electron The Quantum Model of the Atom Electron Cloud file:///D:/student/ch04/sec02/vc03/hc604_02_v03fs.htm file:///D:/student/ch04/sec02/vc01/hc604_0 2_v01fs.htm The Quantum Model of the Atom Atomic Orbitals and Quantum Numbers Quantum numbers specify the properties of atomic orbitals and the properties of electrons in orbitals 4 quantum numbers Principal Quantum Number (1st) The principal quantum number, symbolized by n , indicates the main energy level occupied by the electron Values of n are positive integers – 1, 2, 3, 4, and so on An n increases, the electron’s energy and distance from nucleus increases Principal Quantum Number e- is further from the nucleus n=1 n=2 n=3 n=4 n=5 n=6 n=7 Angular Momentum Quantum Number (2nd) l The angular momentum quantum number, symbolized by , indicates the shape of the orbital Value of 0, 1, 2, 3 and Represented by four sublevels ( s, p, d, f ) More about the 2nd Quantum # l 0 1 2 3 lettershape s p d f sphere dumbell dumbells + dumbells ++ s p n=1 n=2 n=3 n=4 n=5 n=6 n=7 d f Magnetic Quantum Number (3rd) The magnetic quantum number, symbolized by m, indicates the orientation of an orbital around the nucleus Values -l to +l S = spherical and centered around nucleus P = dumbbell extended along x, y, z axis D = cloverleaf 1s orbital S spherical 2s and 3s 1p orbital P dumbbell shape 3p, 4p, 5p etc. 2p orbitals similar shapes 3 larger 3 d orbitals D cloverleaf 5 Spin Quantum Number (4th) The spin quantum number has only two possible values - (+1/2 , −1/2) - which indicate the spin of an electron in an orbital Spin Continued Within a particular orbital, there can be two electrons (take the 2s orbital for example) The electrons have 3 of same quantum numbers in the 2s orbital, but cannot have all four (Pauli) Therefore both electrons in this orbital must have different spins (= +1/2 or -1/2) The Quantum Model of the Atom Atomic Orbitals and Quantum Numbers The Quantum Model of the Atom Shapes of s, p, and d Orbitals F orbital (rarely seen at ground state) The Quantum Model of the Atom Electrons Accommodated in Energy Levels and Sublevels The Development of a New Atomic Model Electrons Accommodated in Energy Levels and Sublevels The Development of a New Atomic Model Quantum Numbers of the First 30 Atomic Orbitals Relationships between Quantum Numbers http://wps.prenhall.com/wps/media/objects/4974/5093961 /emedia/ch07/aabxgdc0.html Review 1. What are the shapes of s, p, and d orbitals respectively? s= spherical p = dumbbell d = cloverleaf 2. How many 1s orbitals are there in an atom? 4p orbitals? 4d orbitals? 1s: 1 4p: 3 4d: 5 4. Which orbitals cannot exist? 2p 3p 4d 3f 6s 2d 3f and 2d How many electrons can an energy level of n = 4 hold? (a) 32 (c) 8 (b) 24 (d) 6 Practice 1. 2. 3. 4. 5. 6. On the back of your Periodic Table, write the electron configuration for the following elements: Helium Berilium Nitrogen Carbon Arsenic Iodine