Chemical Bonding

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Chemical Bonding

• Covalent Bonding
• Electron Sharing

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Chemical Bonding

• Ionic Bonding electrons transferred between
  atoms
• Covalent Bonding electrons shared between atoms

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Covalent Bonding

• Atoms will share valence electrons so that both
  will achieve a stable electron configuration
• The attraction between the shared electrons and
  the nuclei of the individual atoms holds the
  atoms together
• One pair of shared electrons is called a single
  covalent bond

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Representing a Covalent Bond
Darker in between nuclei means that electrons
spend more time there
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Molecules

• A electronically neutral group of atoms held
  together by one or more covalent bonds

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Diatomic Molecules

• A molecule that consists of two of the same kind
  of atoms
• H2, F2, N2, Cl2, Br2, I2, O2

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Multiple Bonds

• Some atoms are held together by sharing more than
  one pair of electrons
• Double Bond two atoms share two pairs of
  electrons
• Four electrons total
• Triple Bond two atoms share three pairs of
  electrons
• Six electrons total

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Polar Covalent Bonds

• Some atoms have a greater attraction for
  electrons than other atoms
• When these atoms form a covalent bond, the
  electrons will not be shared equally
• This is referred to as a polar covalent bond

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Polar Covalent Bonds
This means that the hydrogen side of the molecule
a positive charge
Chlorine wants electrons more than hydrogen.
While they share, they share unequally and the
pair of electrons spends more time around
chlorine than hydrogen
This gives the chlorine side of the molecule a
negative charge
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Electronegativity

• Electronegativity is defined as the ability of an
  atom to attract electron density to itself when
  joined to another atom in a chemical bond.
• The most electronegative elements have the
  greatest attraction for electrons
• Pauling assigns values to each atom
• Scale from 0 4

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Electronegativity Differences

• The difference between electronegativity values
  of two atoms determines what kind of bond it is
• gt1.7 Ionic
• Electrons completely transferred
• 0.0 0.4 Nonpolar Covalent
• Electrons shared equally
• 0.4 1.7 Polar Covalent
• Electrons shared unequally

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Attraction Between Polar Compounds
Hydrogen is positive
Hydrogen is positive
The negative part of one water molecule is
attracted to the positive part of another water
molecule
Oxygen is negative
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Nonpolar Covalent Bonds

• Some atoms have similar attraction for electrons,
  so the shared pair(s) will spend equal time
  around each atom
• There are no positive or negative sides
• This is referred to as a nonpolar covalent bond

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General Properties of Covalent Compounds

• Lower Melting Points than ionic compounds
• Cannot conduct electricity (molecules will not
  separate into ions)

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Differences Between Polar and Nonpolar Covalent
Compounds

• Polar Compounds will attract each other SLIGHTLY
• Nonpolar compounds have no attraction for each
  other
• Polar Compounds will have slightly higher melting
  points, but not as high as ionic compounds