Orbital Diagrams, Electron Configuration Notation, Electron-Dot Structures Chapter 5

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Orbital Diagrams, Electron Configuration
Notation, Electron-Dot Structures Chapter 5
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Lecture Objectives

• Give the electron configuration for elements when
  given the Atomic number (in both spectroscopic
  notation and pictorially).
• List for any element the last energy level
  occupied by electrons and the number of electrons
  occupying the energy level.
• Draw a dot diagram of an element to represent the
  valence electrons.

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Aufbau Diagrams

• Uses individual orbitals
• Gives subshell arrangement
• Each orbital takes one electron before any other
  orbital in the same subshell can receive a second
  electron
• Also called an orbital diagram
• e.g. Orbital Diagram for A Nitrogen Atom

N 1s 2s 2p 3s
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Orbital Diagram for A Magnesium Atom

• Mg
• 1s 2s 2p 3s

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Practice Diagram

• Write the orbital diagram for the electrons in
  an oxygen atom.

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Diagram Solution

• Write the orbital diagram for the electrons in
  an oxygen atom.
• 1s 2s 2p 3s

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Practice Diagram

• Write the orbital diagram for the electrons in
  an iron atom.

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Diagram Solution

• Write the orbital diagram for the electrons in
  an iron atom.
• 1s 2s 2p 3s 3p
• 3d

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Electron Configuration

• Spectroscopic notation specifies the shorthand
  for the electrons in an element.
• Quantum number n is the coefficient for each l
  value, and the number of electrons in each
  orbital is indicated by superscript values.
• e.g. The electron configuration for nitrogen is
  1s22s22p3
• e.g. The electron configuration for magnesium is
  1s22s22p63s2

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Practice in Electron Configuration

• What is the Electron Configuration for oxygen?
• 1s22s22p4
• Draw oxygens electron configuration as an
  orbital diagram.
• What is the Electron Configuration for iron?
• 1s22s22p63s23p64s23d6
• Draw irons electron configuration as an orbital
  diagram.

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Valence Electrons

• The valence electrons are the electrons in the
  outermost orbitals of an atom.
• It is only the valence electrons that determine
  the chemical properties of an element.
• The number of valence electrons can easily be
  determined for Groups 1, 2, and 13-18.
• These groups are also called 1A, 2A, and 3A-8A,
  which just happen to represent the total number
  of valence electrons for the elements in each of
  these columns.

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Valence Electrons

• The number of valence electrons is less obvious
  for Group 3-12 elements.
• Look at the electron configuration and determine
  how many electrons are in the last level. This
  works for all elements through vanadium (atomic
  number 23).
• Beyond this, using this method will give the
  incorrect configurations for chromium and copper.
  Well learn why in Chapter 6.

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Electron Dot Diagram

• G.N. Lewis created the electron dot diagram in
  1902 as shorthand for representing the
  all-chemically important valence electrons.
• The elements symbol represents the atomic
  nucleus and inner-level electrons and is
  surrounded by dots representing the valence
  electrons.
• The dots are placed one at a time around the four
  sides of the symbol, and then paired up until all
  8 (the maximum number of valence electrons) are
  used.
• e.g. Li

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Need Quantum Help?

• This website has excellent demonstrations and
  explanations for all of quantum theory.
• http//www.colorado.edu/physics/2000/index.pl?Type
  TOC