Covalent Bonding

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I. The Covalent Bond(p. 240 247)

• Covalent Bonding

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A. Why Do Atoms Bond?

• Gain stability
• Lower potential energy
• Atoms that fulfill the octet rule are more stable

attraction vs. repulsion
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B. What is a covalent bond?

• A chemical bond that results from the sharing of
  electrons
• Molecule two or more atoms
• that are held together by
• covalent bonds
• Majority of covalent bonds form between nonmetals
  (CLOSE together on periodic table)

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Examples

• Which of the following are covalent compounds?
• NaBr
• SiO2
• CO2
• AlCl3
• CH4

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Properties Table
COVALENT
IONIC
e- are transferred from metal to nonmetal
e- are shared between two nonmetals
Bond Formation
Type of Structure
true molecules
crystal lattice
Physical State
liquid or gas
solid
Melting Point
low
high
Solubility in Water
yes
usually not
yes (solution or liquid)
Electrical Conductivity
no
Other Properties
Form electrolytes in solution
odorous
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C. Covalent Bonding Formation

• Diatomic molecule molecule containing only two
  atoms
• Some atoms exist this way because they are more
  stable than the individual atoms

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D. Diatomic Elements

• The Seven Diatomic Elements
• Br2 I2 N2 Cl2 H2 O2 F2

H
N
O
F
Cl
Br
I
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E. Lewis Structures

• Electron Dot Diagrams
• show valence e- as dots
• distribute dots like arrows in an orbital
  diagram
• 4 sides 1 s-orbital, 3 p-orbitals
• EX oxygen

O
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E. Lewis Structures

• Octet Rule
• Most atoms form bonds in order to obtain 8
  valence e-
• Full energy level stability Noble Gases

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E. Lewis Structures

• Example Electron Dot Notations
• Ca
• P
• H
• C

Ca
P
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Lewis Structures w/2 elements

• Single Bonds
• When atoms share one pair of electrons
• The two shared electrons belong to both atoms
  simultaneously
• Lewis Structure dots or a line symbolize a single
  covalent bond (1 pair of shared e-)

H H
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E. Lewis Structures

• How would you draw the Lewis structure for
  fluorine?
• Diatomic!
• F F

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E. Lewis Structures

• Multiple Covalent Bonds
• When atoms share more than one pair of electrons
• Have higher bond energies and are shorter than
  single bonds

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E. Lewis Structures

• Double Bonds
• Sharing two pairs of electrons between two atoms
• Draw Lewis Structures for 2 oxygen atoms

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E. Lewis Structures

• Triple Bonds
• Sharing three pairs of electrons between two
  atoms
• Draw Lewis Structures for 2 nitrogen atoms

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Naming Molecules

• Section 8.2

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C. Molecular Nomenclature

• Prefix System (binary compounds)
• 1. Less e-neg atom comes first.
• 2. Add prefixes to indicate of atoms. Omit
  mono- prefix on first element.
• 3. Change the ending of the second element to
  -ide.

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C. Molecular Nomenclature

• PREFIX
• mono-
• di-
• tri-
• tetra-
• penta-
• hexa-
• hepta-
• octa-
• nona-
• deca-

• NUMBER
• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10

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C. Molecular Nomenclature

• CCl4
• N2O
• SF6

• carbon tetrachloride

• dinitrogen monoxide

• sulfur hexafluoride

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C. Molecular Nomenclature

• arsenic trichloride
• dinitrogen pentoxide
• tetraphosphorus decoxide

• AsCl3

• N2O5

• P4O10

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B. Lewis Structures

• Nonpolar Covalent - no charges
• Polar Covalent - partial charges