11.4 Electron Configurations

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11.4 Electron Configurations

• And the Periodic Table

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11.4 Electron Configurations (p377)

• The electron configuration of hydrogen is 1s1
• This means there is one electron in the 1s
  orbital.

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11.4 Electron Configurations

• Rule 1 Electrons occupy the lowest orbital
  energies first.

2p
Energy
2s
Then here
1s
First here
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11.4 Electron Configurations

• Rule 2 Pauli Exclusion Principle Two electrons
  can occupy the same orbital.
• They have different spins

2p
Energy
2s
1s
One
Two
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11.4 Electron Configurations

• Rule 3 Electrons will not pair up in the same
  orbital until all energy levels are occupied.

2p
Energy
2s
1s
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Example Sodium (Na)

• Start by drawing a dashed line for each
  sub-orbital needed in the correct order.

1s
3s
2px
2s
2py
2pz
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11.4 Electron Configurations

• Look at your field diagram
• The order of the seats is the same as the order
  of orbitals.
• Notice the 4th energy level has seats closer than
  some of the 3rd energy level.
• Which orbital fills up first, 4s or 3d?
• Yes, 3d.

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Electron Configuration

• Quicker way to write the orbital notation
• Example sodium
• Becomes 1s22s22p63s1

1s
3s
2px
2s
2py
2pz
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11.4 Electron Configurations

• Examples Li (Z3), N (7), O(8) (See book)
• Mg can be written as Ne3s2
• Valence electrons are the electrons in the
  highest principal energy level of an atom. They
  are involved in bonding with other atoms.
• Nitrogen has electrons in n 1 and 2. Level 2
  is the valence level. 1s22s22p3
• Nitrogen has 5 valence electrons.

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11.4 Electron Configurations

• The core electrons are the inner electrons, and
  are not involved in bonding.
• Question What elements have the same number of
  valence electrons as N?
• Where are they on the periodic table?
• Elements with the same number of valence
  electrons have similar chemical properties.

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B. Electron Configurations and the Periodic Table.
Helium actually part of s-block
1
2
s-block
3
p-block
d-block Number one less than row number
4
5
6
7
f-block Number two less than row number
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Example Germanium (Ge)

• Do the orbital notation

1s
2s
2p
2p
2p
3s
3p
3p
3p
4s
3d
3d
3d
3d
3d
4p
4p
4p
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11.4 C. Atomic Properties and the Periodic Table

• Representative Elements - groups 1A-8A
• Ionization ionization is when an atom loses an
  electron.
• Remember ______________ lose electrons.
• _______________ gain electrons.
• Going down a group, atoms are more likely to lose
  an electron. Cs is more likely to lose an
  electron than Li.

Metals
Nonmetals
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11.4 C. Atomic Properties and the Periodic Table

• Atomic size decreases going up and right.
• Decreases going up because electrons are closer
  at lower principal energy levels.
• Decreases going right because the charge in the
  nucleus is stronger.

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Atomic Size

• Size generally decreases

• Size generally decreases

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11.4 C. Atomic Properties and the Periodic Table

• Ionization energy - the energy required to remove
  an electron from an atom in the gas phase.
• increases up a group
• increases to the right

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Ionization Energy

• Increases

• increases

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Checkpoint

• Which element has a larger atomic size?
• Sulfur or chlorine?
• Answer Sulfur
• Which element has the larger ionization energy?
• Sodium or potassium?
• Answer Sodium
• http//www.mhhe.com/physsci/chemistry/essentialche
  mistry/flash/atomic4.swf
• http//video.google.com/videoplay?docid-213426665
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