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AP Chemistry: Class 33

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Period E – Monday, November 4th

Chapter 7 Terms

  • valence orbitals
  • effective nuclear charge
  • atomic radius
  • isoelectronic
  • ionization energy
  • electron affinity
  • metallic character

Class Activity – Trends

  • Take a look at the shared spreadsheet [LINK]
  • Note: Google Drive – Lecture & Content – Atomic Property Information
  • Open the “Numbers” app on your iPad
  • Create a graph for each of the columns
    • Z vs IE
    • Z vs AR
    • Z vs IR
  • Be sure and label properly and scale each accordingly
  • Write an explanation for each graph that correlates to the elements
  • NOTE: use as many of the terms from the list above as are appropriate
  • SUBMIT: turn in as a PDF to Dropbox folder, including proper graphs and commentary

Homework

  • Ch. 7 (16, 25, 28, 37, 45, 47, 93) on paper
  • Finish the graphing assignment

Answer

  • the key to the trends is understanding effective nuclear charge
  • Zeff is the “net protons” that can “see through” the full levels in an atom
  • Example
    • Na = 11 protons, 2 full shells (10 electrons) Zeff = 11-10 = 1
    • Mg = 12 protons, 2 full shells (10 electrons) Zeff = 12-10 = 2
    • Atomic radius of Mg < Na because greater pull on outer electrons
    • Ionization energy Mg > Na because greater pull on outer electrons
  • Once there is an electron in a shell then adding more does not increase size – level already exists (analogy = floors in a building: once the floor is built then adding more people doesn’t change overall height of building)
  • Adding a level DOES change average electron distance
    • atomic radius Na > Li (3 levels vs 2 levels with same Zeff)
    • ionization energy Li > Na because electrons close in Li, harder to remove
  • Ion sizes (and ionization energies) are largely determined by the RATIO of protons to electrons
    • size of Mg+2 < Na+1 because Mg has 12 protons and Na has 11 protons (both have 10 electrons)

Information

This entry was posted on 2013-11-03 by in Agenda, APChem and tagged , .

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