Worksheet: Chapter 12 Homework Key

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Worksheet Chapter 12 Homework Key
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1. Determine whether the bond formed between
each of the elements listed below would be ionic
or covalent based on the metallic/nonmetallic
nature of the elements involved.
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1. Determine whether the bond formed between
each of the elements listed below would be ionic
or covalent based on the metallic/nonmetallic
nature of the elements involved.

• (a) Li - O ionic (b) N - F covalent
• (c) Se - Cl covalent (d) B - H covalent
• (e) Cr - I ionic (f) K - Cl ionic

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2. Use the electronegativities table in your
notebook to determine whether the bonds listed
below are ionic, polar covalent or nonpolar
covalent..
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2. Use the electronegativities table in your
notebook to determine whether the bonds listed
below are ionic, polar covalent or nonpolar
covalent.

• (a) Li - O 2.53 (ionic) (b) N - F 1.03 (polar
  covalent)
• (c) Se - Cl 0.35 (polar covalent) (d) B - H 0.19
  (nonpolar covalent)
• (e) Cr - I 0.65 (polar covalent) (f) K - Cl 1.92
  (ionic)

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3. Which bond in question 2 is the strongest?
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3. Which bond in question 2 is the strongest?

• Li - O

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4. List three properties of metals.
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4. List three properties of metals.

• high melting points (solids)
• hard
• conductors
• shiny
• malleable
• lose electrons

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5. Metallic bonds have delocalized electrons.
What are delocalized electrons?
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5. Metallic bonds have delocalized electrons.
What are delocalized electrons?

• Delocalized electrons are electrons which are
  free to drift from one atom to another within a
  metal.

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6. Why do covalent bonds form between elements
with similar electronegativities?
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6. Why do covalent bonds form between elements
with similar electronegativities?

• Elements with similar electronegativities have to
  share electrons because neither atom has enough
  pull on the electrons (electronegativity) to
  capture the electrons from the other atom.

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7. State a difference and a similarity between
polar covalent and nonpolar covalent bonds.
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7. State a difference and a similarity between
polar covalent and nonpolar covalent bonds.

• Polar covalent bonds involve different nonmetal
  atoms whereas nonpolar covalent bonds involve the
  same nonmetal atoms. Electrons are shared in
  both bonds (equal sharing in nonpolar covalent
  and unequal sharing in polar covalent).

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8. Explain why metals are good conductors of
electricity.
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8. Explain why metals are good conductors of
electricity.
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8. Explain why metals are good conductors of
electricity.

• When electricity is applied to a metal the
  delocalized electrons flow through the metal
  creating an electric current.

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9. Why are metals malleable whereas ionic
compounds are brittle?
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9. Why are metals malleable whereas ionic
compounds are brittle?

• When a metal is bent and the atoms slide past one
  another the delocalized electrons rearrange
  themselves to reform bonds when old bonds are
  broken. In an ionic compound the electrons are
  localized creating fixed positive and negative
  ions and when these ions slide past one another
  bonds do not have the ability to reform and the
  substance shatters when ions of like charges get
  next to each other.