Chemical Bonding

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Chemical Bonding

• Unit Five

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SC Standards Covered

• PS-2.5
• Predict the charge that a representative element
  will acquire according to the arrangement of
  electrons in its outer energy level.
• PS-3.3
• Illustrate the difference between a molecule and
  an atom.
• PS-4.1
• Explain the role of bonding in achieving
  chemical stability.
• PS-4.2
• Explain how the process of covalent bonding
  provides chemical stability through the sharing
  of electrons.
• PS-4.3
• Illustrate the fact that ions attract ions of
  opposite charge from all directions and form
  crystal lattices.
• PS-4.4
• Classify compounds as either crystalline (ionic)
  or molecular (covalent) based on whether their
  outer electrons are transferred or shared.

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Warm-up

• Complete the worksheet on valence
• This should only take 5 minutes.

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What is a chemical bond?

• Attraction between two or more atoms
• Interaction between valence electrons

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Why do atoms attract?

• To become more stable!
• What is the magic number?

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Octet Rule

• Atoms want to have 8 valence electrons to be more
  stable
• Atoms will combine when the compound formed is
  more stable than the separate atoms
• Which atoms need less than 8 valence e- to be
  stable?

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Chemical Stability

• An atom is chemically stable when its outer
  energy level is complete.
• Think about your dot diagrams. What do they
  represent?
• What is the dot diagram for sodium?

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How is Stability Reached?

• Atoms will either gain, lose, or share electrons
  to achieve stability.

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Bonding

• Three Types of Chemical Bonds
• Ionic
• Covalent
• Metallic

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Ionic Bonding

• A bond between a metal and a nonmetal

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Why is it called ionic?

• Sodium loses one electron to form a positive ion
  while chlorine gains one electron to form a
  negative ion.
• Electron Transfer

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Common Ions

• Metals form positive ions and
• Nonmetals form negative ions

1
2
3
-3
-2
-1
/-4
Varies Can be 1, 2, or 3
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Properties of Ionic Compounds

• Compounds containing a metal and a nonmetal
• Have high melting points
• Most dissolve in water
• When dissolved in water, they conduct electricity

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Review
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Covalent Bonding

• Bond formed between 2 nonmetals

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Why is it called covalent?

• Covalent essentially means sharing electrons

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Properties of Covalent Compounds

• Compounds of 2 nonmetals
• Have low melting points
• Most do not dissolve in water
• Do not conduct electricity in solution

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Review
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Metallic Bonding

• Bond formed between metal atoms
• Valence electrons move freely

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Properties of Metallic Bonds

• Metals have high melting points
• Metallic bonds are strong
• Good conductors of heat and electricity

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Review