Bohr- Rutherford Model

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Bohr- Rutherford Model
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Rutherford

• Conducted a gold foil experiment to prove that
• Atoms have a positive core (nucleus)
• Electrons are far away from the nucleus
• Electrons are moving at high speeds around the
  nucleus

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Bohr

• Proved that there are definite energy levels
  around the nucleus
• Electrons are in these energy levels (called
  orbitals or shells) around the nucleus
• Energy levels explained role of valence electrons
  in ionic and covalent bonding

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• Both Bohrs and Rutherfords discoveries led to
  the development of the Bohr-Rutherford model of
  showing how electrons orbit the nucleus of every
  element.

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Energy Levels, Orbitals or Shells

• Electrons orbit the nucleus in regions called
  shells.
• Shells are areas that surround the nucleus like
  layers around an onion.
• Each shell is a certain distance away from the
  nucleus. The first shell is closest to the
  nucleus the second is further away.
• Shells are often called orbitals or energy levels.

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• Each shell can hold a certain number of electrons
  and no more.
• The first shell can hold 2 electrons
• The second shell can hold 8 electrons
• The third shell can hold 8 electrons
• The fourth shell can hold 18 electrons

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The First Shell
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The Second Shell
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The Third Shell
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Complete Electron Shell Exercise
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Bohr Rutherford Diagrams for Ions
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Valence Electrons
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• The outer shell is called the valence shell.
• Electrons in the outer shell are therefore called
  valence electrons.
• Valence electrons are important because they
  determine the elements properties and how it
  will react.
• It is only the valence electrons that are
  involved in chemical reactions.

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Electron Dot Diagrams

• Electron dot diagrams (also called Lewis
  diagrams) are useful because they show only the
  valence electrons, since these are the important
  ones anyways used in chemical bonding.
• They include the elements symbol and dots to
  represent the valence electrons.

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Electron Dot Diagrams
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Lewis Dot Diagrams for Ions