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Chapter 6
Chemical Names
and Formulas
Section 6.1
Introduction to
Chemical Bonding
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“Molecules and
Molecular
Compounds”
Elements are the
building blocks of all
substances.
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Compounds are the
result of chemical
combinations of
atoms of different
elements.
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Most elements in
nature exist in
compounds as
molecules.
Only the noble gases
exist as isolated
atoms.
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Molecules are the
smallest electrically
neutral unit of a
substance that still
has all of the
properties of the
substance.
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Monatomic describes
an element, such as
the Noble gases, that
exists as single
atoms.
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Diatomic molecules
are made up of two
atoms of the same
substance.
H2, O2, N2, F2, Cl2, Br2,
and I2
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Ozone, O3 , is a
triatomic molecule.
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Atoms of different
elements combine
chemically to form
compounds.
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In many compounds
the atoms combine
to form molecules,
and are called
Molecular
Compounds.
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Molecular
compounds tend to
have relatively low
melting and boiling
points.
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Many molecular
compounds exist as
gases or liquids at
room temperature.
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Molecules in most
molecular
compounds are
composed of atoms
of two or more
nonmetals (CO, H2O).
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Molecules of a given
molecular compound
are all the same.
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“Ions and Ionic
Compounds”
Not all compounds
are molecules.
Many compounds are
composed of ions.
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Ions are atoms or
groups of atoms that
have a positive or
negative charge.
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An ion forms when
an atom or group of
atoms loses or gains
an electron.
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Electrons are lost or
gained during a
chemical reaction.
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Atoms of metallic
elements tend to
form ions by losing
one or more
electrons.
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Ions formed by loss
of electrons have a
positive charge and
are called cations.
1+
Na
,
2+
Ca
,
3+
Al
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For metallic
elements, the name
of a cation is the
same as the name of
the element.
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Atoms of nonmetallic
elements tend to
form ions by gaining
one or more
electrons.
Cl
,
2O
,
3N
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Ions formed by
gaining electrons
have a negative
charge and are
called anions.
An anion is
A Negative ION.
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The name of the
anion typically
ends in “ide”.
Example:
The
element chlorine as
an anion becomes
chloride.
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Compounds
composed of cations
and anions are called
Ionic Compounds.
+
Na
Cl
+
 NaCl
NaCl is the
ionic compound
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Ionic compounds are
usually composed of
metallic cations and
nonmetallic anions.
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Although they are
composed of ions,
ionic compounds are
electrically neutral.
2+
Mg
+
2S
 MgS
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