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Electron Configuration


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Electron Configuration

  1. 1. Dalton Model 1803 – John Dalton believed that an atom was an indestructible particle with no internal frame. (Billiard Ball Model) Thomson Model 1897 – J.J. Thomson discovers the electron. He believed electrons were embedded in positive charge sphere. (Plum pudding Model) Rutherford Model 1911 – Ernest Rutherford discovers that there is a dense, positively charged nucleus. Electrons go around the nucleus. Bohr Model 1913 – Niels Bohr enhances Rutherford’s model by having electrons move in a circular orbit at fixed distances from the nucleus. The Evolving Atomic Model
  2. 2. Electrons in an Atom <ul><li>According to the Bohr Model , electrons (e-) can only orbit the nucleus in specific, allowed pathways. </li></ul><ul><li>They move toward and </li></ul><ul><li>away from the nucleus by </li></ul><ul><li>“ steps” or discrete </li></ul><ul><li>amounts of energy </li></ul><ul><li>(a quantum) </li></ul><ul><li>that are released or absorbed. </li></ul><ul><li>e- farther from the nucleus have more energy. Those closer to the nucleus have less energy. </li></ul><ul><ul><li> </li></ul></ul><ul><li>Very similar to a ladder. Just as you cannot step on the air between the rungs, an electron cannot exist between the levels . </li></ul>
  3. 3. <ul><li>Ground state : the lowest energy of an atom </li></ul><ul><li>Excited state : higher potential energy state </li></ul><ul><li>Energy absorbed  e - moves to higher state </li></ul><ul><li>Energy emitted  e - moves to lower state </li></ul>Higher excited state Excited state Ground state Energy Excited state Ground state Energy
  4. 5. <ul><li>Hydrogen’s Line </li></ul><ul><li>Emission Spectrum </li></ul>Excited State Ground State Energy (Light) Turn this sideways and it looks like a ladder
  5. 6. Quantum Mechanical Model <ul><li>In 1926, Erwin Schr ö dinger developed an equation that described the behavior of an e- : </li></ul><ul><li>E ψ (x) = [-(h 2 /8 π 2 m)d 2 /dx 2 + V(x)] ψ (x) </li></ul><ul><li>(Don’t worry, you don’t need to know this!!!) </li></ul><ul><li>He believed: </li></ul><ul><ul><li>Electrons are found in discrete energy levels (as Bohr believed) </li></ul></ul><ul><ul><li>BUT, the electron does not move around the nucleus in a fixed orbit </li></ul></ul><ul><ul><li>Ex: propeller blade </li></ul></ul><ul><li>This all led to the modern quantum theory … </li></ul><ul><ul><li> </li></ul></ul>
  6. 7. Modern Atomic Theory <ul><li>Orbitals describe the three dimensional space that electrons occupy. </li></ul><ul><li>The location of an electron can only be described by probability. (ex. You in this classroom and your parents are looking for you.) </li></ul><ul><li>Orbitals give shape to the atom. </li></ul><ul><li>These properties allow us to describe electrons in terms of their energy and position. </li></ul><ul><li>Ahhh Yes….. Quantum Mechanics! </li></ul>Orbital Not an Orbit
  7. 8. <ul><li>Quantum Mechanics ….Sounds Scary!!!! </li></ul><ul><li>Think of it this way… </li></ul><ul><li>It is the “address” of an electron </li></ul><ul><li>Did you ever mail a letter? </li></ul><ul><li>Where do you live? (4 things) </li></ul><ul><ul><ul><li>State </li></ul></ul></ul><ul><ul><ul><li>City </li></ul></ul></ul><ul><ul><ul><li>Street Name </li></ul></ul></ul><ul><ul><ul><li>House Number </li></ul></ul></ul><ul><li>Electrons are identified the same way ( 4 things )… </li></ul><ul><ul><ul><li>Principle (identified by 1,2,3,4 ) </li></ul></ul></ul><ul><ul><ul><li>Orbital (identified by s, p, d or f ) </li></ul></ul></ul><ul><ul><ul><li>Magnetic </li></ul></ul></ul><ul><ul><ul><li>Spin </li></ul></ul></ul>Abby Lehman 346 W. Palm Street Los Angeles, CA 13543
  8. 9. <ul><li>Four Quantum Numbers </li></ul><ul><li>1. Principle Quantum Number </li></ul><ul><ul><ul><li>Indicates the main energy level occupied by the e- (distance from the nucleus) </li></ul></ul></ul><ul><ul><ul><li>Shell Number (1 st shell is closest to nucleus, 2 nd is further, and so on …) </li></ul></ul></ul><ul><ul><ul><li>Values of n can only be positive integers (1, 2, 3, etc.) </li></ul></ul></ul><ul><li>2. Orbital Quantum Number </li></ul><ul><ul><ul><li>Indicates the shape of the orbital (actual 3D space where the probability of finding e- is greatest) </li></ul></ul></ul><ul><ul><ul><li>Sublevel of n </li></ul></ul></ul><ul><ul><ul><li>Designated s, p, d, f </li></ul></ul></ul>s p d 1 2 3
  9. 10. <ul><li>s sublevel </li></ul><ul><ul><li>S pherical shaped </li></ul></ul><ul><ul><li>One orbital </li></ul></ul><ul><ul><li>Holds two e- </li></ul></ul><ul><li>p sublevel </li></ul><ul><ul><li>P eanut or dumbbell shaped </li></ul></ul><ul><ul><li>Three orbitals </li></ul></ul><ul><ul><li>Holds six e- </li></ul></ul><ul><li>d sublevel </li></ul><ul><ul><li>D ouble peanut shaped </li></ul></ul><ul><ul><li>Five orbitals </li></ul></ul><ul><ul><li>Holds ten e- </li></ul></ul><ul><li>f sublevel </li></ul><ul><ul><li>F lower shaped </li></ul></ul><ul><ul><li>Seven orbitals </li></ul></ul><ul><ul><li>Holds fourteen e- </li></ul></ul>
  10. 11. <ul><li>There are a few rules that help us represent the arrangement of electrons in atoms address </li></ul><ul><li>Aufbau (“building up”) principle : an electron occupies the lowest energy possible </li></ul><ul><li>Hund’s rule : orbitals of equal energy are each occupied by one electron before accepting a second electron </li></ul><ul><li>Pauli exclusion principle : no two electrons in the same atom will have the same set of quantum numbers (no two fans have the same seat) </li></ul>e - How do you write this address for the electron?
  11. 12. <ul><li>To write electron configurations, you need to know: </li></ul><ul><li>Period # 1 – 7 (exception for d orbitals – 1 less) </li></ul><ul><li>Subshell letter (e.g. s, p, d, f…) </li></ul><ul><li>Atomic # is # of e - as an exponent </li></ul>Electron Configurations – Quick address s d p f Example Sulfur = 1s 2 2s 2 2p 6 3s 2 3p 4
  12. 13. Study guide for chp. 4 and 5 Atomic structure notes -Know how to calculate atomic mass -Know how to draw bohr model Review worksheets 4.1-4.3 Know what ion an element will form Quantum mechanics notes Know how to write long hand electron configuration Be able to explain the behavior of electrons (i.e., what did you learn from the flame lab?) Review worksheets 5.1-5.2
  13. 14. Need to add Relate outer shell to lewis dot and oxidation states