Electronic Configuration

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Electronic Configuration
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Energy Levels

• Energy levels are called principal energy levels
  and are given numbers 1, 2, 3, 4, 5
• These principal energy levels contain sub-levels
  which are assigned the letters s, p, d
  and f

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4f
4d
4
4p
4s
Energy
3d
3p
3
3s
2p
2
2s
1
1s
4
Each type of sub-level can hold a different
number of electrons
Sub-level Maximum number of e-
s 2
p 6
d 10
f 14
5
4f14
4d10
4
4p6
4s2
Energy
3d10
3p6
3
3s2
2p6
2
2s2
1
1s2
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Electron Orbitals

• Electrons are constantly moving, however,
  orbitals are regions where is it highly likely an
  electron might be found
• The energy sub-levels are made up of orbitals,
  each of which can hold a maximum of 2 e-.

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Electron Orbitals

• The orbitals in different sub-levels have
  different shapes

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Each orbital can hold 2 e-.
The p sub-shell contains 6 e-
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Each type of sub-level can hold a different
number of electrons
Sub-level Maximum number of e- Number of orbitals
s 2 1
p 6 3
d 10 5
f 14 7
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Energy Levels
Orbital
4p
Energy
3d
4s
3p
3s
Sub- levels
2p
2s
Principal Energy levels
1s
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Drawing Electron Configurations

• Electrons are drawn as single headed arrows.
• The direction of the arrows represent the spin of
  the electron

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Hunds Rule

• Electrons occupy orbitals as unpaired e-. The e-
  are only paired when there are no more empty
  orbitals available in that sub-level. This is
  Hunds Rule
• Paired electrons will have opposite spin as this
  reduces the mutual repulsion between the paired
  e-.

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Energy Level Diagrams
4p
Energy
3d
4s
3p
3s
2p
2s
Na 11e-
1s2, 2s2, 2p6, 3s1
1s
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Order of filling sub-shells
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Energy Level Diagrams
4p
Energy
3d
4s
3p
3s
2p
2s
1s
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Anomalous Electron Configurations

• Chromium has the electron configuration
• 1s2 2s2 2p6 3s2 3p6 3d5 4s1
• NOT 1s2 2s2 2p6 3s2 3p6 3d4 4s2
• The outer sub-level is half full, this is a more
  stable arrangement.

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Anomalous Electron Configurations

• Copper is
• 1s2 2s2 2p6 3s2 3p6 3d10 4s1
• NOT 1s2 2s2 2p6 3s2 3p6 3d9 4s2
• The outer sub-level is full, this is a more
  stable arrangement.

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Electronic Structure of Ions

• Positive Ions formed by the loss of e-
• Na Atom Naion
• 1s2 2s2 2p6 3s1 1s2 2s2 2p6
• Negative Ions formed by the gain of e-
• O Atom O2- ion
• 1s2 2s2 2p4 1s2 2s2 2p6

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Structure of Transition Metal Ions

• With the transition metals it is the 4s electrons
  are lost first when they form ions
• Ti 1s2 2s2 2p63s2 3p6 3d24s2
• Ti2 1s2 2s2 2p63s2 3p6 3d2
• Cr 1s2 2s2 2p63s2 3p6 3d54s1
• Cr3 1s2 2s2 2p63s2 3p6 3d3