2.Electronic Structure

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2.Electronic Structure

  1. 1. ATOMIC STRUCTURE S.MORRIS 2006 More free powerpoints at www.worldofteaching.com
  2. 2. ATOMIC STRUCTURE the number of protons in an atom the number of protons and neutrons in an atom He 2 4 Atomic mass Atomic number number of electrons = number of protons
  3. 3. ELECTRONIC STRUCTURE Electrons are arranged in Energy Levels or Shells around the nucleus of an atom. <ul><li>first shell a maximum of 2 electrons </li></ul><ul><li>second shell a maximum of 8 electrons </li></ul><ul><li>third shell a maximum of 8 electrons </li></ul>
  4. 4. ELECTRONIC STRUCTURE There are two ways to represent the atomic structure of an element or compound; 1. Electronic Configuration 2. Dot & Cross Diagrams (Lewis Diagrams)
  5. 5. G.N. Lewis (1875 -1946) <ul><li>American physical chemist known for the discovery of the covalent bond . </li></ul><ul><li>1916 paper &quot;The Atom and the Molecule“. </li></ul><ul><li>An atom of an element is represented by the symbol for that element. The electrons in the outer shell are shown as dots, small circles or crosses . </li></ul><ul><li>He wrote: “ An electron may form part of the shell of two different atoms and cannot be said to belong to one or other exclusively”. </li></ul>
  6. 6. ELECTRONIC CONFIGURATION With electronic configuration elements are represented numerically by the number of electrons in their shells and number of shells. For example; N Nitrogen 7 14 2 in 1 st shell 5 in 2 nd shell configuration = 2 , 5 2 + 5 = 7
  7. 7. ELECTRONIC CONFIGURATION Write the electronic configuration for the following elements; Ca O Cl Si Na 20 40 11 23 8 17 16 35 14 28 B 11 5 a) b) c) d) e) f) 2,8,8,2 2,8,1 2,8,7 2,8,4 2,3 2,6
  8. 8. DOT & CROSS (LEWIS) DIAGRAMS With Dot & Cross diagrams elements and compounds are represented by Dots or Crosses to show electrons, and circles to show the shells. For example, N; Nitrogen N X X X X X X X N 7 14
  9. 9. DOT & CROSS (LEWIS) DIAGRAMS Draw the Dot & Cross diagrams for the following elements; O Cl 8 17 16 35 a) b) O X X X X X X X X Cl X X X X X X X X X X X X X X X X X X
  10. 10. SUMMARY (Copy and complete) <ul><li>The ------ Number of an atom = number of </li></ul><ul><li>------- in the nucleus. </li></ul><ul><li>The Atomic ---- of an atom = number of </li></ul><ul><li>Protons + Neutrons in the -------. </li></ul><ul><li>The number of Protons = Number of ---------. </li></ul><ul><li>--------- orbit the ------- in shells . </li></ul><ul><li>Each shell can only carry a set number of ---------. </li></ul>
  11. 11. SUMMARY <ul><li>The Atomic Number of an atom = number of </li></ul><ul><li>protons in the nucleus. </li></ul><ul><li>The Atomic Mass of an atom = number of </li></ul><ul><li>Protons + Neutrons in the nucleus. </li></ul><ul><li>The number of Protons = Number of Electrons. </li></ul><ul><li>Electrons orbit the nucleus in shells . </li></ul><ul><li>Each shell can only carry a set number of electrons. </li></ul>

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