Chapter 4 Electron Configurations

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Chapter 4 Electron Configurations
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Pauli Exclusion Principle

• No two electrons in an atom can have the same
  four quantum numbers.

3
Aufbau principle

• An electron occupies the lowest-energy orbital
  that can receive it.

4
Hunds Rule

• Orbitals of equal energy are each occupied by one
  electron before any orbital is occupied by a
  second electron, and all electrons in singly
  occupied orbitals must have the same spin

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Principal Quantum Number

• Generally symbolized by n, it denotes the shell
  (energy level) in which the electron is located.
• Number of electrons that can fit in a shell2n2

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Angular Momentum Quantum Number

• The angular momentum quantum number, generally
  symbolized by l, denotes the orbital (subshell)
  in which the electron is located

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Magnetic Quantum Number

• The magnetic quantum number, generally symbolized
  by m, denotes the orientation of the electrons
  orbital with respect to the three axes in space.

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Spin Quantum Number

• Spin quantum number denotes the behavior
  (direction of spin) of an electron within a
  magnetic field.
• Possibilities for electron spin
• 1/2 or 1/2

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Orbital filling table
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• Electron configuration of the elements of the
  first three series

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Irregular confirmations of Cr and Cu
Chromium steals a 4s electron to half fill its
3d sublevel
Copper steals a 4s electron to FILL its 3d
sublevel
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4.3 Electron Configuration

• 3 rules for adding electrons to orbitals
• Aufbau principle an electron occupies the
  lowest-energy orbital hat can receive it
• Pauli exclusion principle no two electrons in
  the same atom can have the same set of four
  quantum numbers
• Hunds rule orbitals of equal energy are each
  occupied by one electron before any orbital is
  occupied by a second electron, and all electrons
  in singly occupied orbital must have the same
  spin

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Representing electron configuration

• The electron configuration for boron is 1s22s22p1
• How many electrons are present in an atom of
  boron?
• What is the atomic number?
• Write the orbital notation for boron
• ?? ?? ? ___ ___
• 1s 2s 2px 2py 2pz

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Practice write the electron configuration
notation for nitrogen

• ?? ?? ? ? ?
• 1s 2s 2px 2py 2pz

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Orbital Notation

• Write the orbital notation for Carbon
• __ __ __ ___ ___
• 1s 2s 2px 2py 2pz

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Noble Gas Configuration

• This is a short hand notation
• Ne3s23p1 for the element Al

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Homework

• Read section 4.3
• Pg 116 section review 1-5
• Pg 118 18, 19, 20, 23, 24