CHEMICAL BONDING

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CHEMICAL BONDING

• CHAPTER 12

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GENERAL OVERVIEW

• Understand and classify the types of bonds that
  bind atoms / molecules together
• Explain how the valence electron arrangement of
  an atom contributes to the types of bonds formed
• Use models to understand the 3-D structure of
  atoms / molecules and how that structure affects
  chemical and physical properties

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TYPES OF CHEMICAL BONDS

• BOND a force that holds groups of two or more
  atoms or molecules together
• BOND ENERGY the energy required to break a
  chemical bond a measurement of the strength of a
  bond

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TYPES OF CHEMICAL BONDS

• IONIC BOND a bond formed between oppositely
  charged ions the strongest kind of chemical bond
• Ex NaCl ? Na Cl-
• COVALENT BOND a bond in which valence electrons
  are shared equally between two atoms
• Ex H2 (See Fig. 12.1, Pg 342)

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TYPES OF CHEMICAL BONDS

• POLAR COVALENT BOND a type of covalent bond in
  which valence electrons are unequally shared
  between two atoms
• Ex H F
• d d-
• (See Fig. 12.2, Pg 343)
• The Greek symbol, delta, d, is used to indicate a
  partial charge.
• Note that d is the lower case Greek symbol and
  is different from the uppercase, ?, which is used
  to indicate change.

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ELECTRONEGATIVITY

• ELECTRONEGATIVITY the relative ability of an
  atom to attract electrons to itself. (Fig. 12.3,
  Pg 344)
• Atomic Radius Decreases ? Ionization Energy
  Increases ? Electronegativity Increases

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ELECTRONEGATIVITY

• The polarity of a chemical bond depends on the
  difference between the electronegativity values
  of the atoms forming the bond.
• In general, if atoms have the same
  electronegativity values the bond is covalent.
  If the values are different the bond is polar
  covalent. If the values are very different the
  bond is ionic.
• (See Table 12.1, Pg 344 and Fig. 12.4, Pg 345)

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BOND POLARITY AND DIPOLE MOMENTS

• DIPOLE MOMENT Polar covalent molecules are said
  to have a dipole moment, that is, a center of
  positive charge and a center of negative charge.
• This charge distribution, based on the differing
  electronegativities of the atoms, is represented
  with an arrow where arrow is directed toward the
  center of negative charge. (Fig. 12.5, Pg 346)