Electrons are shared

1
Electrons are shared

• Covalent Bonds

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How do you identify a covalent formula?

• All Nonmetals in formula

3
Why do atoms form bonds?

• To get the configuration of a noble gas

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Shape of all diatomics?

• Linear

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Shape of NH3, NF3, PH3, etc?

• Pyramid

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Shape of H2O, H2S, H2Se, etc.?

• Bent

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How do you make a Lewis Dot Structure?

• Arrange the symbols
• Count up the valence electrons
• Distribute the valence electrons, starting with
  the bonding pairs single bonds
• Tests

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Shape of CH4, CCl4, etc.?

• Tetrahedral

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Polar

• Has poles the ends are different!

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Polar

• Electronegativity Difference is 0.5 to 1.7

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Nonpolar

• No poles. Ends are the same.

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Nonpolar

• Electronegativity difference 0 to 0.5

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Ionic

• Electronegativity difference ? 1.7

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Ionic

• Extremely polar

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Ionic

• Formula has a metal and a nonmetal

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WATER

• Polar. Water is bent. The O end is a bit
  negative the H end is a bit positive.

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Bonding

• Results from attractions between nucleus on 1
  atom electrons on another atom.

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Making a bond

• releases energy.

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Breaking a bond

• Absorbs energy.

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Covalent Compounds are

• Molecular compounds.

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N2

• Triple Bond

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O2

• Double Bond

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When bonds are made, energy is

• released.

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When bonds are broken, energy is

• absorbed.

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As the energy of a system ?, the stability
generally

• increases.

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Exothermic

• System releases energy. Its energy level goes
  down.

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Properties of Molecular Substances

• Soft
• Low melting point low boiling point
• Does not conduct electricity in any phase
• Does not dissolve in water
• React slowly

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Nonpolar Bonds

• Electrons are shared equally between the two atoms

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Molecular Polarity

• Molecule must contain polar bonds and they must
  be arranged asymmetrically.

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Molecular Polarity

• Depends on the shape
• (Bent Pyramidal are polar
• Linear tetrahedral, polarity depends on
  composition.)

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Nonpolar Molecules

• Noble gas atoms (kickballs)
• Diatomics of the form A2 (footballs)
• Larger molecules that have high symmetry

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Polar Molecules

• Diatomics of the form AB
• Larger molecules that have low symmetry

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Nonpolar Molecules

• Weak Intermolecular Forces
• (Dispersion or Van der Waals)
• Low boiling points melting points
• Tend to be gases

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Polar Molecules

• Intermolecular Forces are Dipole-dipole forces
• Stick together easier than nonpolar molecules

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Coordinate Covalent Bond

• Covalent bond where both electrons in the bond
  are donated by 1 atom.

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Coordinate Covalent Bond

• H
• HNH
• H

HNH H
..
..
H
?
..
..
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Coordinate Covalent Bond

• Both electrons in the bond are donated by the
  same atom.

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Compound that exhibits both covalent ionic
bonding

• Compound that contains a polyatomic ion.

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How to calculate the polarity of a bond

• Subtract the electronegativities of the 2 atoms.