1 / 93

Chapter 6: Electronic Structure of Atoms

Chapter 6: Electronic Structure of Atoms. Light is a form of electromagnetic radiation (EMR) :. an oscillating charge, such as an electron, gives rise to electromagnetic radiation:. Electric Field. Magnetic Field. Chapter 6: Electronic Structure of Atoms.

zea
Download Presentation

Chapter 6: Electronic Structure of Atoms

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 6: Electronic Structure of Atoms Light is a form of electromagnetic radiation (EMR): • an oscillating charge, such as an electron, gives rise to electromagnetic radiation: Electric Field Magnetic Field

  2. Chapter 6: Electronic Structure of Atoms • Both the Electric and the Magnetic field propagate through • space • In vacuum, both move at the speed of light(3 x 108 m/s)

  3. Chapter 6: Electronic Structure of Atoms • Electromagnetic radiation is characterized by • wavelength (), or frequency () and • amplitude (A) l A = intensity l l

  4. Chapter 6: Electronic Structure of Atoms Frequency (n) measures how many wavelengths pass a point per second: 4 xl ÷ 1 s = 4 s-1= 4 Hz 1 s

  5. Chapter 6: Electronic Structure of Atoms Electromagnetic radiation travels at the speed of light: c = 3 x 108 m s-1 Relation between wavelength, frequency, and amplitude: c =l n

  6. Chapter 6: Electronic Structure of Atoms The Electromagnetic Spectrum 400 nm 750 nm

  7. wavelength (l) frequency (n) energy (E) Chapter 6: Electronic Structure of Atoms RedOrangeYellowGreenBlueUltraviolet

  8. Chapter 6: Electronic Structure of Atoms A certain type of laser emits green light of 532 nm. What frequency does this wavelength correspond to?

  9. Chapter 6: Electronic Structure of Atoms Photoelectric Effect Albert Einstein (1879-1955) e- e- e-

  10. Chapter 6: Electronic Structure of Atoms Photoelectric Effect Albert Einstein (1879-1955) e- e- e- e- • Light of a certain minimum frequency is required to dislodge electrons from metals

  11. Max Planck (1858 - 1947) Chapter 6: Electronic Structure of Atoms frequency E = h  Planck’s constant = 6.63 x 10-34 J s

  12. Chapter 6: Electronic Structure of Atoms • Energy of light is related to its frequency, not intensity E = h  • light comes in “units” or packets of “h” • Intensity is related only to the number of “units” • The h “unit” is called a quantum of energy • A quantum of light (EMR) energy = photon

  13. Chapter 6: Electronic Structure of Atoms Electromagnetic Radiation stream of particles (photons) wave or E = h n Whether light behaves as a wave or as a stream of photons depends on themethod used to investigate it !

  14. Chapter 6: Electronic Structure of Atoms Relationship between Energy, Wavelength, and Frequency:

  15. Chapter 6: Electronic Structure of Atoms What is the energy of a photon of light of 532 nm? = 3.74 x 10-19 J

  16. Chapter 6: Electronic Structure of Atoms Understanding light in terms of photons helped understand atomic structure many light sources produce a continuous spectrum

  17. Chapter 6: Electronic Structure of Atoms Thermally excited atoms in the gas phase emit line spectra continuous spectrum (all wavelengths together: white light) line spectrum (only some wavelengths: emission will have a color)

  18. Rydberg constant 1.097 x 107 m-1 positive integers (e.g. 1,2,3, etc) Chapter 6: Electronic Structure of Atoms Photograph of the H2 line spectrum (Balmer series) in the visible region (1825-1898) Johann Balmer (1825-1898)

  19. Chapter 6: Electronic Structure of Atoms Thermally excited atoms in the gas phase emit line spectra continuous spectrum (all wavelengths together: white light) line spectrum (only some wavelengths: emission will have a color)

  20. Chapter 6: Electronic Structure of Atoms Niels Bohr was the first to offer an explanation for line spectra Bohr Model of the Hydrogen Atom • Only orbits of defined energy and radii are permitted in the hydrogen atom • Energy is absorbed or emitted by the electron as the electron moves from one allowed orbit into another. Energy is absorbed or emitted as a photon of E = hn

  21. (1885-1962) Chapter 6: Electronic Structure of Atoms Niels Bohr was the first to offer an explanation for line spectra electron orbits n = 1 n = 2 n = 3 n = 4 n = 5 n = 6 nucleus Bohr’s Model of the Hydrogen Atom

  22. n = 6 n = 5 n = 4 n = 3 n = 2 n = 1 Chapter 6: Electronic Structure of Atoms Bohr’s Model of the Hydrogen Atom Energy absorption of a photon e Ground State nucleus

  23. n = 6 n = 5 n = 4 n = 3 n = 2 n = 1 Chapter 6: Electronic Structure of Atoms Bohr’s Model of the Hydrogen Atom Energy “excited state” e Ground State nucleus

  24. n = 6 n = 5 n = 4 n = 3 n = 2 n = 1 Chapter 6: Electronic Structure of Atoms Bohr’s Model of the Hydrogen Atom Energy e Ground State nucleus

  25. n = 6 n = 5 n = 4 n = 3 n = 2 n = 1 Chapter 6: Electronic Structure of Atoms Bohr’s Model of the Hydrogen Atom Energy e Ground State emission of a photon nucleus

  26. n = 6 n = 5 n = 4 n = 3 n = 2 n = 1 Chapter 6: Electronic Structure of Atoms Which of these transitions represents an absorption process? a [b and c are emission processes] (a) (b) (c) Energy Which of these transitions involves the largest change in energy? c Which of these transitions leads to the emission of the longest wavelength photon? b smallest distance = lowest energy = long l Ground State Does this wavelength correspond to a high or low frequency? long l = low energy = low frequency nucleus

  27. Transitions corresponding to the Balmer series n=3 → n=2 n=4 → n=2 n=6 → n=2 n=5 → n=2 Chapter 6: Electronic Structure of Atoms

  28. Chapter 6: Electronic Structure of Atoms

  29. Energy of electron in a given orbit: n = 6 n = 5 n = 4 n = 3 n = 2 n = 1 Chapter 6: Electronic Structure of Atoms n = Principal Quantum Number (main energy levels) h=Planck’s constant, c=speed of light, RH = Rydberg constant

  30. n = 6 n = 5 n = 4 n = 3 n = 2 n = 1 Chapter 6: Electronic Structure of Atoms For an electron moving from n = 4 to n = 2: DE = - 4.09 x 10-19 J energy decreases = emission of a photon

  31. n = 6 n = 5 n = 4 n = 3 n = 2 n = 1 Chapter 6: Electronic Structure of Atoms The energy of the photon emitted is: E = 4.09 x 10-19 J What wavelength (in nm) does this energy correspond to? l = 486 x 10-9 m = 486 nm

  32. n=3 → n=2 n=4 → n=2 n=6 → n=2 n=5 → n=2 Chapter 6: Electronic Structure of Atoms Balmer Series l = 486 nm

  33. Chapter 6: Electronic Structure of Atoms The Uncertainty Principle Werner Heisenberg (1901-1976) and Niels Bohr

  34. Chapter 6: Electronic Structure of Atoms The Uncertainty Principle It is impossible to know both the exact position and the exact momentum of a subatomic particle

  35. Chapter 6: Electronic Structure of Atoms Quantum Mechanics and Atomic Orbitals Erwin Schrödinger (1887-1961)

  36. Chapter 6: Electronic Structure of Atoms Quantum Mechanics and Atomic Orbitals • Schrödinger proposed wave mechanical model of the atom • Electrons are described by a wave function, ψ • The square of the wave function, ψ2, provides information on • the location of an electron (probability density or electron density)

  37. Chapter 6: Electronic Structure of Atoms Quantum Mechanics and Atomic Orbitals • the denser the stippling, the • higher the probability of finding • the electron • shape of electron density • regions depends on energy of • electron

  38. z y x Chapter 6: Electronic Structure of Atoms Bohr’s model: n = 1 orbit electron circles around nucleus Schrödinger’s model: orbital n = 1 or electron is somewhere within that spherical region

  39. Chapter 6: Electronic Structure of Atoms Bohr’s model: • requires only a single quantum number (n) to describe an orbit Schrödinger’s model: • requires three quantum numbers (n, l, and m) to describe an orbital n: principal quantum number l : second or azimuthal quantum number ml: magnetic quantum number

  40. - energy of electron in a given orbital: Chapter 6: Electronic Structure of Atoms Schrödinger’s model: (1) n = principal quantum number (analogous to Bohr model) - the higher n, the higher the energy of the electron - is always a positive integer: 1, 2, 3, 4 ….

  41. - lis normally listed as a letter: Value of l: 0 1 2 3 letter: spdf Chapter 6: Electronic Structure of Atoms Schrödinger’s model: (2)l = azimuthal quantum number - takes integral values from 0 to n-1 e.g. n = 3 l = 0, 1, 2 - ldefines the shape of an electron orbital

  42. p-orbital (1 of 3) d-orbital (1 of 5) f-orbital (1 of 7) Chapter 6: Electronic Structure of Atoms Schrödinger’s model: z y x s-orbital

  43. Chapter 6: Electronic Structure of Atoms Schrödinger’s model: (3) ml = magnetic quantum number - takes integral values from -lto +l, including 0 e.g. l = 2 ml= -2, -1, 0, 1, 2 - mldescribes the orientation of an electron orbital in space

  44. n=3 shell 4f subshell Chapter 6: Electronic Structure of Atoms 3 n = 1 2 4 l = 0 0, 1 0, 1, 2 0, 1, 2, 3 1s 2s, 2p 3s, 3p, 3d 4s, 4p, 4d, 4f ml = 0; -1,0,1; 0 -1,0,1 -2,-1,0,1,2 -3,-2,-1,0,1,2,3 0; 0; -1,0,1; -2,-1,0,1,2; # orbitals in subshell 1 1 3 3 5 1 3 5 1 7 Total # of orbitals in shell 1 4 9 16

  45. Chapter 6: Electronic Structure of Atoms 3s-room 3p-room 3deluxe-room 3rd floor 2s-room 2promotion-room 2nd floor standard-room 1st floor

  46. Chapter 6: Electronic Structure of Atoms Orbital energy levels in the Hydrogen Atom

  47. Chapter 6: Electronic Structure of Atoms Representation of Orbitals 1s 2s 3s

  48. Chapter 6: Electronic Structure of Atoms Representation of Orbitals s-orbital

  49. Chapter 6: Electronic Structure of Atoms Representation of Orbitals p-orbitals

  50. Chapter 6: Electronic Structure of Atoms Representation of Orbitals d-orbitals

More Related