Electrons

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Electrons

• Valence Electrons
• Bohr Models
• Lewis Dot Structures

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Valence Electrons

• The electrons in the outer most electron shell
  are called valence electrons
• The number of valence electrons is the same as
  the group number

1 2   3 4 5 6 7 8
1 2 3 4 5 6 7 8
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Valence Electrons

• Valence electrons are the electrons that are
  available for reactions with other elements.
• Octet Rule - For atoms to be happy they must
  gain, lose or share electrons until they have 8
  valence electrons
• This is why atoms bond to be happy!
• An element with a full valence shell is a happy
  element ?
• Noble gases are usually unreactive
• This is because they have full valence shells

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Becoming An Ion

• Electrons are negatively charged
• Protons are positively charged
• Neutral atoms do not have a charge because the
  number of protons is the same as the number of
  electrons
• When atoms gain or lose electrons (to become
  happy) they become positively or negatively
  charged
• An atom with a charge is called an Ion

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Common Charges of Ions
1 2   3 4 -3 -2 -1 0
1 2 3 4 -3 -2 -1 0
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Bohr Models

• Niels Bohr created a visual model of the atom to
  make them easy to understand
• A Bohr Model contains a central nucleus
  surrounded by electron shells
• For each model you state the element in the
  nucleus and draw a dot on the electron shells for
  each electron

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Lewis Dot Structures

• electron-dot structure consists of elements
  symbol surrounded by dots that represent the
  atoms valence e