Valence Electrons

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Valence Electrons Bohr Diagrams
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Atomic Structure

• Atoms have a nucleus that contains Protons and
  Neutrons
• Electrons are contained in shells that surround
  the nucleus
• An atom is made of mostly empty space
• Protons have a positive charge
• Electrons have a negative charge
• Neutrons are Neutral

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Bohr - Rutherford diagrams

• Putting all this together, we get B-R diagrams
• To draw them you must know the of protons,
  neutrons, and electrons (2,8,8,2 filling order)
• Draw protons (p), (n0) in circle (i.e.
  nucleus)
• Draw electrons around in shells

He
Li
Li shorthand
3 p 4 n0
2 p 2 n0
Draw Be, B, Al and shorthand diagrams for O, Na
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Valence Electrons

• Each electron shell can hold a certain number of
  electrons
• Electron shells are filled from the inside out
• Noble Gases have full outer electron shells
• All other elements have partially filled outer
  electron shells

Electron Shell Number of Electrons
1 2
2 8
3 8
4 18
5 18
6 32
7 32
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Valence Electrons

• The electrons in the outer most electron shell
  are called valence electrons
• The shell containing electrons that is furthest
  from the nucleus is called the valence shell
• The number of electron shells with electrons is
  the same as the period number

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Noble Gas Stability

• Noble gases are usually unreactive
• This is because they have full valence shells
• An element with a full valence shell is a happy
  element ?
• For two atoms to join together atoms must gain,
  lose or share electrons
• Elements with full valence shells do not easily
  gain or lose electrons

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Noble Gas Stability

• Atoms want to gain stability
• Atoms will try to gain or lose electrons to have
  a full valence shell
• Metals try to lose electrons
• Non-Metals try to gain electrons

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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 they become
  positively or negatively charged
• An atom with a charge is called an Ion

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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 number of protons
  and neutrons in the nucleus and draw a dot on the
  electron shells for each electron