Covalent Bonding

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Covalent Bonding
Goal Make models of covalent compounds

• Review Lewis diagrams for ionic compounds
• Draw dot structures for the ff
• Iron (II) fluoride b. potassium chloride c.
  hydrogen sulfide
• Discussion on covalent bonding

..\Chemistry\Bonding\Covalent Bonding.ppt

• Model Making Covalent Compounds

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A covalent bond exists when two electrons are
shared by two non-metallic atoms.
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COVALENT BONDING
Sharing of electrons in outer energy levels to
gain stability
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Examples of Covalent Bonding
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HYDROGEN
H
H
H
H
HYDROGEN MOLECULE
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Refer to the following key for the color of the
atoms.
Element Colors Green.. Chlorine Wooden Pegs 1 inch - carbon to hydrogen or chlorine 2 inches- carbon to carbon or nitrogen/others Helical springs for multiple bonds (double or triple bonds)
Yellow Hydrogen Orange. Sodium Wooden Pegs 1 inch - carbon to hydrogen or chlorine 2 inches- carbon to carbon or nitrogen/others Helical springs for multiple bonds (double or triple bonds)
Red .. Oxygen Purple.. Potassium Wooden Pegs 1 inch - carbon to hydrogen or chlorine 2 inches- carbon to carbon or nitrogen/others Helical springs for multiple bonds (double or triple bonds)
Black .. Carbon Blue Nitrogen Wooden Pegs 1 inch - carbon to hydrogen or chlorine 2 inches- carbon to carbon or nitrogen/others Helical springs for multiple bonds (double or triple bonds)
Formula Count Atoms Draw and Color Model Dot Structure
H2 2 hydrogen atoms H H (structural formula) H H (dot structure)
Cl2 2 chlorine atoms
CH4
CCl4
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PROPERTIES

• low melting and boiling points

Weak IMF of attraction between simple molecules

• generally, do not dissolve in water

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• generally, do not conduct electricity when
  molten or dissolved in water

do not contain ions
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ALLOTROPHY
Elements exist in two or more forms in the same
physical state
POLYMORPHISM
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COVALENT STRUCTURES
Simple Molecular few atoms Strong IntraM bonds Weak InterM bonds
Giant Molecular thou-sands of atoms diamond graphite plastics
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TESTS

1. Physical Appearance
2. Smell (Fanning)
3. Gentle Heating
4. Solubility Test
5. Conduction of electricity

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Tetrahedral Arrangement
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GRAPHITE
Layered structure
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GLASSES AND CERAMICS
Super-cooled liquid
Made up of Kaolinite
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Formula

• Shorthand method for writing compound names.
• Uses element symbols
• Uses subscripts beside element symbol to indicate
  number of atoms of each element present in a
  molecule of the compound
• Example
• CH4
• Carbon 1 atom
• Hydrogen 4 atoms

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Examples of Covalent Compounds
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METHANE (CH4)
6C 2,4
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AMMONIA (NH3)
7 N 2,5
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WATER
8O 2,6
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CARBON DIOXIDE
O C O
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Properties of Covalent Bonds

• Lower melting and boiling points when compared to
  ionic compounds
• Atoms held together by weak forces.
• Molecules in solids held closely together.
• Generally poor conductors of electricity

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Polar Covalent Bonds

• Unequal sharing of electrons in covalent bond
  which causes one end of the molecule to be
  slightly positive and one end to be slightly
  negative.

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Nonpolar Covalent Bonds
Equal sharing of valence electrons in a covalent
bond.