Arrangement of Electrons in Atoms

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Arrangement of Electrons in Atoms

• 4-3 Electron Configurations

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Electron Configuration

• Describes where the electrons are found and what
  energies they possess.
• They are determined by distributing the atoms
  electrons among levels, sublevels, and orbitals
  based on a set of principles.

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Determining Electron Configurations

• They fill using the Aufbau Principle
• Electrons in atoms want to assume the lowest
  possible energy.
• Ground-state electron configuration

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Order Orbitals are filled
Note 4s fills before 3d, this is what is found
in nature. The energy levels get closer together
farther from nucleus.
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Pauli Exclusion

• Pauli Exclusion Principle
• An orbital can hold a maximum of 2 electrons.
• 2 electrons in the same orbital must have
  opposite spins.
• An electron is "paired" if it is sharing an
  orbital with another electron with an opposite
  spin.
• An electron is "unpaired" if it is alone in an
  orbital

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Hunds Rule

• Electrons occupy equal-energy orbitals so that a
  maximum number of unpaired electrons results.
• You must put a single electron in each
  equal-energy orbital before you begin to pair.

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Short Cut to remembering order.either one works
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Sample 1
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Sample 2
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You try

• Write the configurations for A) magnesium and B)
  Nickel. How many unpaired electrons does each
  possess?

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• A) Mg 1s22s22p63s2 No unpaired
• B) Ni 1s22s22p63s23p64s23d8 Two Unpaired

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We will learn this chart later