Electron Configurations

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Electron Configurations

• 03/28/12

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N. Bohr1913

• Electrons travel in definite paths.
• Electrons jump between levels
• from path to path.

Bohr Model of the Atom
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Electron Energy Levels

• Any of the several different regions in which
  electrons travel about the nucleus.
• As electrons increase in energy, they occupy
  energy levels farther from the nucleus.

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Bohr Diagram

• First energy level is filled with 2 electrons.
• Second energy level is filled with 8 electrons
• Third energy level is filled with 18 electrons

1st energy level
2nd energy level
3rd energy level
P N
Nucleus
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Valence electrons

• Outermost energy level of an atom is called
  valence shell.
• Electrons in valence shell are called valence
  electrons.
• Group number indicates the number of valence
  electrons.

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How do you determine the number of energy levels?

• Period number determines the number of energy
  levels.
• Example Sodium is in period 3, so it has 3
  energy levels

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Electron configurations

• Boron Atomic number 5, Mass number 11
• Number of protons number of electrons 5

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Example - Sodium

• Atomic number 11, Mass number 23

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Example - Calcium

• Atomic number 20, Mass number 40

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Practice
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Practice
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Practice
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Practice