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Periodic Trends


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Periodic Trends

  1. 1. November 18 th & 19 th , 2009 Periodic Trends
  2. 2. Periodic Law <ul><li>When elements are arranged in order of increasing atomic #, elements with similar properties appear at regular intervals (periodically). </li></ul>
  3. 3. Periodic Properties <ul><li>Atomic Radius </li></ul><ul><ul><li>Size of atom </li></ul></ul><ul><li>First Ionization Energy </li></ul><ul><ul><li>Energy required to remove one e - from a neutral atom. </li></ul></ul><ul><li>Electronegativity </li></ul><ul><ul><li>How much an atom pulls </li></ul></ul><ul><ul><li>Electrons towards itself in a bond </li></ul></ul>© 1998 LOGAL © 1998 LOGAL
  4. 4. Atomic Radius <ul><li>Size of atom </li></ul>Li Ar Ne K Na
  5. 5. Atomic Radius <ul><ul><li>Increases to the LEFT and DOWN </li></ul></ul><ul><ul><ul><li>Francium is the largest atom </li></ul></ul></ul>
  6. 6. Atomic Radius <ul><li>Why larger going down? </li></ul><ul><ul><li>Higher energy levels have larger orbitals </li></ul></ul><ul><li>Why smaller to the right? </li></ul><ul><ul><li>Shielding – core electrons block the attraction between the nucleus and the valence electrons </li></ul></ul><ul><ul><li>Increased nuclear charge without additional shielding pulls electrons in tighter </li></ul></ul>
  7. 7. Ionization Energy <ul><li>Energy required to remove an electron </li></ul><ul><li>It ALWAYS requires some energy to remove an electron!! </li></ul>K Na Li Ar Ne He
  8. 8. Ionization Energy <ul><ul><li>Increases UP and to the RIGHT </li></ul></ul><ul><ul><li>Helium has the highest Ionization Energy </li></ul></ul>
  9. 9. Ionization Energy <ul><li>Why opposite of atomic radius? </li></ul><ul><ul><li>In small atoms, e - are close to the nucleus where the attraction is stronger and they are harder to pull off </li></ul></ul><ul><ul><ul><li>Small atom = high ionization energy </li></ul></ul></ul><ul><ul><li>In larger atoms, the valence electrons are easier to pull off </li></ul></ul><ul><ul><ul><li>Large atom = low ionization energy </li></ul></ul></ul>
  10. 10. Electronegativity <ul><li>Ability of an atom to pull electrons towards itself in a bond. </li></ul>
  11. 11. <ul><ul><li>Increases UP and to the RIGHT </li></ul></ul><ul><ul><li>Fluorine has the highest electronegativity </li></ul></ul><ul><ul><li>Noble gases have no electronegativity because they don’t form bonds </li></ul></ul>Electronegativity
  12. 12. Electronegativity <ul><li>Why opposite of atomic radius? </li></ul><ul><ul><li>In small atoms, there is less shielding so the protons pull harder on electrons </li></ul></ul><ul><ul><ul><li>Small atom = high electronegativity </li></ul></ul></ul><ul><ul><li>In larger atoms, there is more shielding </li></ul></ul><ul><ul><ul><li>Large atom = low electronegativity </li></ul></ul></ul>
  13. 13. Examples <ul><li>Which atom has the larger radius? </li></ul><ul><ul><li>Be or Ba </li></ul></ul><ul><ul><li>Ca or Br </li></ul></ul><ul><ul><li>Ba </li></ul></ul><ul><ul><li>Ca </li></ul></ul>
  14. 14. Examples <ul><li>Which atom has the higher Ionization Energy? </li></ul><ul><ul><li>N or Bi </li></ul></ul><ul><ul><li>Ba or Ne </li></ul></ul><ul><ul><li>N </li></ul></ul><ul><ul><li>Ne </li></ul></ul>
  15. 15. Examples <ul><li>Which atom has the higher electronegativity? </li></ul><ul><ul><li>Li or C </li></ul></ul><ul><ul><li>Cr or Kr </li></ul></ul><ul><ul><li>C </li></ul></ul><ul><ul><li>Kr? </li></ul></ul>