Molecular Compounds (a.k.a. Covalent Compounds)

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Molecular Compounds (a.k.a. Covalent Compounds)
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Ionic Compounds Review

• Ionic compounds are the combination of ions. E.g.
  Na Cl- ? NaCl.
• This formula represents the __________ of sodium
  ions and chloride ions not the exact number of
  them.
• They are composed of a ___________________ and
  form a crystal structure (e.g. NaCl and CaCl2
  which are both salts)

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Molecular Compounds

• Consist of atoms covalently bonded together
• The elements involved are all __________

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Some examples

• N2O ? _____________ Gas used at the dentist to
  relax patients
• NO2 ? _____________ poisonous toxin emitted
  from car exhaust

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More Examples

• H2O ? ______
• CO2 ? ____________ Gas
• exhaled and created during
• combustion reactions
• CO ? ____________________ Lethal gas created
  during incomplete combustion

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Recall

• In ionic compounds, the non-metal rips away the
  electron(s) from the metal because the metals
  loosely hold their electrons
• This creates a positive and negative ion which
  attract each other making them stick together
  (opposites attract)

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• Molecular Compounds
• made up of a non-metal
• and a non-metal.
• also called _____________

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• Molecular Compounds
• ________ electrons (e-) to form a
  ________________.
• Neg. e- are attracted to the Pos. nuclei of both
  atoms

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Molecular Compounds

• Molecular compounds are formed when non metals
  share electrons to fill their outer electron
  orbit (shell).
• If we draw the Lewis Structure for Fluorine,
• We can see that it needs ________
• It wants to share one electron with another atom.
• If it bonds with another fluorine atom
• We draw the shared pair of electrons between the
  two atoms.

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Molecular Compounds

• Many molecular compounds are predictable.
• How will Oxygen bond with Hydrogen to form a
  molecule.
• Draw the Lewis Structure of both Atoms.
• ________________________
• Clearly we need another Hydrogen atom
• Putting the shared electrons between the atoms.
• The molecule is H2O

The Oxygen atom has 8 valence electrons (full)
and the Hydrogen has 2 valence electrons (full)
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Molecular Compounds

• Not all molecular compounds are as predictable.
• How will Oxygen bond with Carbon?
• Draw the Lewis Structures of each atom.
• ___________________________
• If we add one more Oxygen, each oxygen can share
  two.
• However, if Oxygen will share two and donate one
  of its other electrons pairs, Oxygen can bond
  with just on Carbon atom.

_____________
_____________
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Types of Bonds
Water Single bond because ______ pair of
electrons are shared
Carbon Monoxide Triple Bond because
_______pairs of electrons are shared
Carbon Dioxide Double bond because _______pairs
of electrons are shared
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Molecular Compounds Naming

• So Oxygen can form CO or CO2
• We need a more flexible naming system for
  covalent compounds to reflect the many different
  bonding possibilities.
• To name a covalent compound,
• Starting with the atom that is to the left in the
  periodic table, (or lower)
• Write the name of the atoms with the prefix
  indicating the number of that atom in the
  compound.
• Change the ending of the last atom to ide.

• The prefixes are,
• _______
• _______
• _______
• _______
• _______
• _______
• _______
• Note, the mono is omitted on the first atom.
• CO _____________
• CO2 _____________

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Memorize me!
Number Prefix Number Prefix
1 mono 6 _________
2 _________ 7 hepta
3 tri 8 _________
4 _________ 9 nona
5 penta 10 _________
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Naming Example

• P4O10
• ?Phosphorus - use prefix tetra (4)
• ?Oxygen change ending Oxide
• ?Oxide use prefix deca (10)
• _________

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Molecular Compounds - Naming

• Name the following compounds
• CF4
• _________
• H2O
• _________
• PF5
• _________

• Write the chemical formula for,
• Sulphur Dioxide
• _________
• DiCarbon Tetrahydride
• _________

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Molecular Compounds Diatomic Gases

• Molecular compounds show an incredible variety in
  structure, physical and chemical properties.
• There are categories that further divide covalent
  compounds into categories with common properties.

• Diatomic Gases _________
• The Halogens, Oxygen, Nitrogen and Hydrogen form
  diatomic gases.
• H2 is called Hydrogen Gas not Dihydrogen.

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• Eg. N2 - _________
• O2 - _________
• 
  Air

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Writing Formulas

• ?left-most element goes 1st
• Carbon monoxide
• Carbon (C) ? no prefix therefore C
• - Monoxide Mono 1 therefore, 1 oxygen atom
  O
• _________

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Writing Formulas

• Nitrogen dioxide
• Nitrogen (N) ? no prefix therefore N
• - Dioxide Di 2 therefore, 2 oxygen atoms
  O2
• _________

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Writing Formulas

• DiCarbon Tetrahydride
• Dicarbon (C) ? Di 2 therefore C2
• - Tetrahydride (H) ? Tetra 4 therefore, 4
  Hydrogen atoms H4
• _________

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Exceptions that need to be Memorized!

• CH4 _________
• H2O2 _________
• H2O Water

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These Too!

• NH3 _________
• O3 _________