VIII. Electron Configurations

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					VIII. Electron Configurations
  Energy      Types of          Total          Total
 Level (n)    orbitals       number of      number of
                             Orbitals in   electrons in
                               energy         energy
                              level (n2)    level (2n2)
    1              s             1              2
    2            s, p            4              8
    3           s, p, d          9             18
    4         s, p, d, f         16            32
    5        s, p, d, f, g       25            50
    6        s,p,d,f,g,h         36            72
VIII. Electron Configurations
• Within an energy level,

         s<p<d<f<g<h<i
   Lowest energy            Highest energy
VIII. Electron Configurations
             1s
             2s 2p
Increasing   3s 3p 3d
Energy
             4s 4p 4d 4f
             5s 5p 5d 5f 5g
             6s 6p 6d 6f 6g 6h
             7s 7p 7d 7f 7g 7h 7i
VIII. Electron Configurations
• Remember:
  – Each orbital can only hold 2 electrons
  – Every energy level that has p orbitals must
    contain 3 of them
  – Every energy level that has d orbitals must
    contain 5 of them
  – Every energy level that has f orbitals must
    contain 7 of them
VIII. Electron Configurations
Example:
• Into which orbitals would the 20
  electrons in a calcium (Ca) atom go?

• First, there are rules governing how
  electrons must occupy the orbitals (see
  bottom of Aufbau Diagram handout).
  MEMORIZE THEM.
VIII. Electron Configurations
Example:
• Aufbau Principle: electrons must occupy
  the lowest energy orbitals first.
• Hund’s Rule: no two electrons can have
  the same set of 4 quantum numbers
  – Electrons in the same orbital must have
    opposite spins
VIII. Electron Configurations
Example:
• Pauli Exclusion Principle: When
  electrons occupy degenerate orbitals,
  one electron must occupy each orbital
  (spins parallel) before they can start
  pairing up.
VIII. Electron Configurations
    Example: (20 electrons)

         4s
         3d

E        3p
         3s
         2p

         2s

         1s
VIII. Electron Configurations
    Look at your Aufbau Diagram handout

         3d
         4s

E        3p
         3s
         2p

         2s

         1s
     VIII. Electron Configurations
 • How do we write these without having to
   use the diagram every time (save space)?

 • Orbital notation:
     – Horizontal Aufbau diagram



1s     2s     2p   2p    2p    3s   3p   3p   3p


4s
VIII. Electron Configurations
• How do we write these without having to
  use the diagram every time (save
  space)?

• Electron Configuration notation:
  – Lists each energy level and orbital TYPE
    (superscript indicated total number of
    electrons in each type of orbital)
                1s22s22p63s23p64s2
  – NOTE: do NOT use commas
VIII. Electron Configurations
• Example:
  – Use the Aufbau diagram to write the
    electron configuration for arsenic (As)
VIII. Electron Configurations

    4p
    3d
    4s

E   3p
    3s
    2p

    2s

    1s
VIII. Electron Configurations
• Example:
  – Use the Aufbau diagram to write the
    electron configuration for arsenic (As)

           1s22s22p63s23p64s23d104p3
VIII. Electron Configurations
• Example:
  – Use the Aufbau diagram to write the
    electron configuration for all the noble
    gases
  – He: 1s2
  – Ne:1s22s22p6
  – Ar: 1s22s22p63s23p6
  – Kr: 1s22s22p63s23p64s23d104p6
  – Xe: 1s22s22p63s23p64s23d104p65s24d105p6
  – Rn:
    1s22s22p63s23p64s23d104p65s24d105p66s2
   14   10   6
VIII. Electron Configurations
• Notice there are other deviations from
  the expected order.
• How can you memorize this pattern (so
  you can duplicate the Aufbau diagram)?
VIII. Electron Configurations
             1s
             2s 2p
Increasing   3s 3p 3d
Energy
             4s 4p 4d 4f
             5s 5p 5d 5f 5g
             6s 6p 6d 6f 6g 6h
             7s 7p 7d 7f 7g 7h 7i

				
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