Atoms, Elements, and Compounds

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Atoms, Elements, and Compounds
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Chapter Fifteen Molecules and Compounds

• 15.1 Compounds and Chemical Bonds
• 15.2 Electrons and Chemical Bonds

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Investigation 15A
Chemical Bonds

• How do atoms form chemical bonds with other
  atoms?

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15.1 Compounds and chemical bonds

• A compound contains two or more different
  elements that are chemically bonded together.

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15.1 Compounds and chemical bonds

• A mixture contains two or more elements and/or
  compounds that are not chemically bonded
  together.

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15.1 Molecules and covalent bonds

• A chemical bond forms when atoms transfer or
  share electrons.
• A covalent bond is formed when atoms share
  electrons.

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15.1 Chemical formulas and diagrams

• Molecules are represented by a chemical formula.
• The chemical formula tells you the precise number
  of each kind of atom in the molecule.

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15.1 Structure and function

• The properties of a compound depend MUCH more on
  the exact composition and structure (shape) of
  its molecule than on the elements of which it is
  made.

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15.1 Ionic bonds

• Ionic bonds are bonds in which electrons are
  transferred from one atom to another.
• Sodium and chlorine form an ionic bond because
  the positive sodium ion is attracted to the
  negative chloride ion.

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15.1 Why chemical bonds form

• It takes energy to separate atoms that are bonded
  together.
• The same energy is released when chemical bonds
  form.
• Atoms form bonds to reach a lower energy state.

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