Chemistry 105 Laboratory
Name:___________________
LABORATORY 7: CHEMICAL BONDING
Atoms form bonds with other atoms in order to achieve stability, 8 valence electrons. This is the Octet rule.
Types of bonds
There are 2 ways that atoms form bonds.
Sharing electrons :
Covalent Bonds
Transferring electrons :
Ionic Bonds
Covalent Bonds:
When 2 nonmetal atoms share at least one pair of electrons a covalent bond is formed
Lewis dot diagrams of diatomic elements:
Hydrogen
Chlorine
Oxygen
Nitrogen
HONC Rule
The most bonds between any two atoms is:
Lewis dot diagrams of diatomic some simple compounds:
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Water
Carbon dioxide
Ammonia
Methane
Carbon tetrachloride
Carbon monoxide
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Ionic Bonds:
When a metal atom and a nonmetal atom react they form a bond in which the metal atom loses one or
more electrons and the nonmetal atom gains one or more electrons. The bond is the attraction between
a negative ion and a positive ion.
Ion an atom or molecule that has a charge due to gaining or losing an electron
Cations: Positively charged ions. Atoms that have lost an electron leaving more protons in the nucleus
than there are electrons
Anions: Negatively charged ions. Atoms that have gained an electron leaving more electrons than
protons in the nucleus.
Examples
Sodium chloride
Magnesium oxide
Calcium bromide
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Electronegativity: how attracted an atom is towards the electrons in a bond
Patterns of electronegativity on the periodic table
High electronegativity elements
Low electronegativity elements
Electronegativty and chemical bonds
Ionic bonds
Covalent bonds
Polar covalent
Nonpolar covalent
Types of Molecules
Just as bonds can be polar or nonpolar, molecules can also be polar or nonpolar. This polarity
significantly affects the properties of the molecule.
Nonpolar molecules:
Polar Molecules:
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Intermolecular bonds:
Bonds can form between atoms of different molecules or molecules and ions. These bonds are not as
strong as the covalent and ionic bonds.
Ion-dipole attractions between an ion and the partially charged part of a polar molecule
Hydrogen bond A hydrogen bond is a relatively strong dipole-dipole attractive force between a
hydrogen atom and a pair of nonbonding electrons on a F,O, or N atom
Dipole-dipole interactions are electrostatic attractions between polar molecules
London Forces London forces are very weak electrostatic forces of attraction between molecules with "temporary"
dipoles.
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Purpose: To make models of organic compounds
Procedure and Observations and Data:
1.
Building molecules (This is to be done in groups of 2)
Obtain the molecular modeling kits from the stockroom
1. Build the following molecules and draw the structure after you have built it. Show each model to
your instructor before you take it apart. Do not take them apart until you have the initials.
H2
N2
O2
Cl2
I2
H 2O
NH3
Instructor’s Initials__________________________
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CH4
Name:
CCl4
Name:
C2H6
Name:
C3H8
Name:
C8H18
Name:
CO2
C2H5OH
Name:
Instructor’s Initials__________________________
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Show 2wo different ways to make C4H10
Name:
Name:
Show two different ways to make C3H7Cl
Name:
Name:
Show 3 different ways to make C5H12
Name:
Name:
Name:
Instructor’s Initials__________________________
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Show how to make C2H4
Name:
Make a benzene ring C6H6
Instructor’s Initials__________________________
Organize your atoms and bonds as they were when you checked them out. Return them to the stockroom.
Questions and Answers:
1.
How do you know if a compound is ionic or covalent by looking at the formula?
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2.
What are the properties of ionic compounds?
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3.
What are the properties of covalent compounds?
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Conclusions and Reflections
1. Did you learn better by building models of the molecules? Why?
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2.
Write two questions you have about chemical bonding.
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3.
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Are all covalent bonds equal?
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4. How can we measure if there are differences?
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