CHAPTER 8
Compounds
and
Molecules
8.2 Molecular
Compounds
In early chapters we discussed
physical and chemical properties
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In later chapters we discussed atom
structures and chemical bonding
8.2 Molecular Compounds
Physical
and
chemical
properties
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Atom
structures
and
chemical
bonding
8.2 Molecular Compounds
Ionic
compounds
(like table
salt, NaCl)
Physical
and
chemical
properties
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First we addressed
ionic compounds
Atom
structures
and
chemical
bonding
8.2 Molecular Compounds
Now we will address
molecular compounds
which are held together by
covalent bonds.
Physical
and
chemical
properties
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Molecular
compounds
(like DNA)
Atom
structures
and
chemical
bonding
8.2 Molecular Compounds
Properties of molecular compounds vary widely
Hardness
Some are hard and brittle; some are flexible, soft or mushy
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8.2 Molecular Compounds
Properties of molecular compounds vary widely
Hardness
Some are hard and brittle; some are flexible, soft or mushy
State of matter
They can be solid, liquid or gas at room temperature
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8.2 Molecular Compounds
Properties of molecular compounds vary widely
Hardness
Some are hard and brittle; some are flexible, soft or mushy
State of matter
They can be solid, liquid or gas at room temperature
Boiling points
Their boiling points can vary from –253oC to over 1,000oC
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8.2 Molecular Compounds
Properties of molecular compounds vary widely
Hardness
Some are hard and brittle; some are flexible, soft or mushy
State of matter
They can be solid, liquid or gas at room temperature
Boiling points
Their boiling points can vary from –253oC to over 1,000oC
Ability to conduct electricity
Most do not conduct electricity well
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8.2 Molecular Compounds
Water
Water is a covalent compound
About eight million billion billion
(1024) water molecules make up
this cup of water
Properties of molecular substances
depend on:
- the structure of the individual molecule
- the attractions between molecules
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8.2 Molecular Compounds
Molecules can be classified into different categories
Small
Caffeine,
found in tea, coffee,
and soda
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Medium
Wax,
one of the main
hydrocarbons in beeswax
8.2 Molecular Compounds
Molecules can be classified into different categories
Large: polymer
Protein,
molecule on the right shows a thick
line tracing the linear chain with red
and blue marking either end
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Large: network
Graphene,
layers of which make
graphite
8.2 Molecular Compounds
Small molecules
Most small molecules
(no more than a dozen
atoms) are liquids or gases
at room temperature
Some of the most
important molecules
related to our ecosystem
are small molecules
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Acetaminophen
(Tylenol)
is a liquid at room temperature
8.2 Molecular Compounds
Most small molecules
(no more than a dozen
atoms) are liquids or gases
at room temperature
Some of the most
important molecules
related to our ecosystem
are small molecules
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If ice did not float, ponds would freeze
from the bottom up, killing everything
inside.
Water
8.2 Molecular Compounds
Small molecules
Ethene
(or ethylene)
Ethanol
Nonpolar (gas at room temperature)
Boiling point = –103.7oC
Polar (liquid at room temperature)
Boiling point = 78.4oC
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8.2 Molecular Compounds
Medium-sized molecules
Medium-sized molecules
(no more than 100 atoms)
tend to be liquids or soft
solids at room temperature.
They are often long-chain
hydrocarbons or lipids
Candle wax is a mixture of
medium-sized hydrocarbons
hydrocarbon: a molecule made entirely from carbon and
hydrogen atoms.
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8.2 Molecular Compounds
Medium-sized molecules
Lipids are typically fats or steroids
Fats are nonpolar and insoluble in
water
Linoleic acid, a major
component of vegetable oil
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8.2 Molecular Compounds
Medium-sized molecules
Most steroids have four
rings of carbon atoms.
3
1
They can act as
hormones, drugs,
vitamins, or poisons
4
2
Testosterone
(a steroid)
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8.2 Molecular Compounds
Polymers
Polyvinyl chloride (PVC) is made by bonding
many vinyl chloride monomers together
A single monomer of
vinyl chloride
A single polymer chain typically contains
hundreds to thousands of atoms
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8.2 Molecular Compounds
Polymers
Recycling symbols and polymer codes
Polyvinyl chloride
polymer: a long chain molecule formed by connecting
small repeating units with covalent bonds.
monomer: a small molecule that is a building block of
larger molecules called polymers.
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8.2 Molecular Compounds
Polymers
Starch fragment
found in food (bread, pasta…)
Glucose
a natural monomer
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8.2 Molecular Compounds
Polymers
Starch fragment
found in food (bread, pasta…)
Glucose
a natural monomer
Cellulose fragment
makes up wood, paper…
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8.2 Molecular Compounds
Polymers
Starch fragment
Homopolymers are made from only
one type of monomer
Glucose
a natural monomer
Cellulose fragment
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8.2 Molecular Compounds
Polymers
Copolymers are made from more
than one type of monomer
adenine
thymine
guanine
cytosine
sugarphosphate
backbone
nucleotides
DNA fragment
a heteropolymer
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8.2 Molecular Compounds
Polymers
Most proteins are made from
up to 20 different monomers
called amino acids
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8.2 Molecular Compounds
Polymers
Most proteins are made from
up to 20 different monomers
called amino acids
Four of these bind
together to form
hemoglobin, the protein
complex in blood cells
that transports oxygen
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8.2 Molecular Compounds
Networks
Silicon dioxide (or quartz)
is a mineral in sand
Since every atom in quartz is covalently bonded
together, the entire grain can be considered a
single network.
network covalent: a type of large structure, usually made
from hundreds to billions of atoms, in which each atom is
covalently bonded to multiple neighboring atoms, forming
a web of connections.
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8.2 Molecular Compounds
Networks
Carbon forms many types of network covalent substances
Diamond
Buckyballs
Carbon nanotubes
Graphite
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8.2 Molecular Compounds
Chemical formulas
Use the empirical formula to describe
the simplest ratio of elements of that
substance
A sample of ionic or network covalent
substance is a single bonded unit of
material
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8.2 Molecular Compounds
Chemical formulas
Use the empirical formula to describe
the simplest ratio of elements of that
substance
a molecule of water
A sample of ionic or network covalent
substance is a single bonded unit of
material
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Use the molecular formula to
indicate the exact type and
number of each atom in a single
molecule of that substance
8.2 Molecular Compounds
Chemical formulas
a molecule of water
Benzene
Empirical formula: CH
Molecular formula: C6H6
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Use the molecular formula to
indicate the exact type and
number of each atom in a single
molecule of that substance
8.2 Molecular Compounds
Chemical formulas
Write the molecular formula for each of the following molecules:
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8.2 Molecular Compounds
Chemical formulas
Write the molecular formula for each of the following molecules:
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Asked:
The molecular formula
Relationships:
The formula should reflect the exact number and type of
atoms in an individual molecule of the substance.
8.2 Molecular Compounds
Chemical formulas
Write the molecular formula for each of the following molecules:
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Asked:
The molecular formula
Relationships:
The formula should reflect the exact number and type of
atoms in an individual molecule of the substance.
Solve:
A. C2H2
8.2 Molecular Compounds
Chemical formulas
Write the molecular formula for each of the following molecules:
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Asked:
The molecular formula
Relationships:
The formula should reflect the exact number and type of
atoms in an individual molecule of the substance.
Solve:
A. C2H2
B. NH3
8.2 Molecular Compounds
Chemical formulas
Write the molecular formula for each of the following molecules:
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Asked:
The molecular formula
Relationships:
The formula should reflect the exact number and type of
atoms in an individual molecule of the substance.
Solve:
A. C2H2
B. NH3
C. C2H5O
8.2 Molecular Compounds
Naming simple molecular compounds
Naming organic molecules
can be complex
Binary molecular
compounds have
simpler names
Carbon dioxide
2-benzyl-1,1-dichlorocyclobutane
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8.2 Molecular Compounds
Naming simple molecular compounds
Consider the following molecular compound:
P2S3
two phosphorous atoms
with three sulfur atoms
diphosphorous trisulfide
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8.2 Molecular Compounds
Naming simple molecular compounds
Consider the following molecular compound:
H2O
two hydrogen atoms
with one oxygen atom
?
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8.2 Molecular Compounds
Naming simple molecular compounds
Consider the following molecular compound:
H2O
two hydrogen atoms
with one oxygen atom
dihydrogen monoxide
(another name for water)
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8.2 Molecular Compounds
Naming simple molecular compounds
Consider the following molecular compound:
CO
Drop
“mono”
for
the
first
element
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one carbon atom
with one oxygen atom
carbon monoxide
8.2 Molecular Compounds
Naming simple molecular compounds
Write the name for each of the following formulas: N2O4, S2F10, and SO3.
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8.2 Molecular Compounds
Naming simple molecular compounds
Write the name for each of the following formulas: N2O4, S2F10, and SO3.
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Asked:
Names of the formulas
Given:
Three formulas and a table of prefix names
Relationships:
The name of the formula is constructed from the simple ionic
name with prefixes before each element, indicating the
number of each atom.
8.2 Molecular Compounds
Naming simple molecular compounds
Write the name for each of the following formulas: N2O4, S2F10, and SO3.
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Asked:
Names of the formulas
Given:
Three formulas and a table of prefix names
Relationships:
The name of the formula is constructed from the simple ionic
name with prefixes before each element, indicating the
number of each atom.
Solve:
N2O4 is dinitrogen tetraoxide.
8.2 Molecular Compounds
Naming simple molecular compounds
Write the name for each of the following formulas: N2O4, S2F10, and SO3.
Asked:
Names of the formulas
Given:
Three formulas and a table of prefix names
Relationships:
The name of the formula is constructed from the simple ionic
name with prefixes before each element, indicating the
number of each atom.
Solve:
N2O4 is dinitrogen tetraoxide.
S2F10 is disulfur decafluoride.
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8.2 Molecular Compounds
Naming simple molecular compounds
Write the name for each of the following formulas: N2O4, S2F10, and SO3.
Asked:
Names of the formulas
Given:
Three formulas and a table of prefix names
Relationships:
The name of the formula is constructed from the simple ionic
name with prefixes before each element, indicating the
number of each atom.
Solve:
N2O4 is dinitrogen tetraoxide.
S2F10 is disulfur decafluoride.
SO3 is sulfur trioxide.
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8.2 Molecular Compounds
Properties of molecular compounds vary widely
Hardness
Some are hard and brittle; some are flexible, soft or mushy
State of matter
They can be solid, liquid or gas at room temperature
Boiling points
Their boiling points can vary from –253oC to over 1,000oC
Ability to conduct electricity
Most do not conduct electricity well
‹#›
8.2 Molecular Compounds
Properties of molecular compounds vary widely
Small molecules
Ethene (or ethylene)
helps fruits to ripen
Nonpolar (gas at room temperature)
Boiling point = –103.7oC
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Acetaminophen
(Tylenol)
Ethanol
(or ethyl alcohol)
Polar (liquid at room temperature)
Boiling point = 78.4oC
8.2 Molecular Compounds
Properties of molecular compounds vary widely
Small molecules
Medium-sized molecules
They are often long-chain
hydrocarbons or lipids
Lipids are typically
fats or steroids
Candle wax (a mixture of
medium-sized hydrocarbons)
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Testosterone
8.2 Molecular Compounds
Properties of molecular compounds vary widely
Small molecules
polymerization
n
Medium-sized molecules
Large molecules
Polymer
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8.2 Molecular Compounds
Properties of molecular compounds vary widely
Small molecules
polymerization
n
Medium-sized molecules
Large molecules
Polymer
Network
Covalent networks
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8.2 Molecular Compounds
Properties of molecular compounds vary widely
Small molecules
Medium-sized molecules
Large molecules
Polymer
Network
P2S3
two phosphorous atoms
with three sulfur atoms
Naming simple molecular compounds
diphosphorous trisulfide
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8.2 Molecular Compounds