Three Types of Bonding
(1) Metallic
(2) Ionic
(3) Covalent
Metallic Bonding
The valence electrons of metal
atoms can be modeled as a
sea of electrons.
Sea of electrons model used
to explain bonding between
metal atoms; it is also
useful in explaining
characteristics of metals
(they conduct electricity,
are maleable, are ductile,
etc.)
The model involves a positively
charged kernel (nucleus and
nonvalence electrons) and valence
electrons that are free to move or
drift freely from one part of the
metal to another. In this model the
valence electrons are mobile.
Metallic bonds consist of the
attraction of the free-floating
valence electrons for the positively
charged kernel of the metal atom
7.3
Metallic Bonds and Metallic Properties
• Metals are ductile—that is,
they can be drawn into
wires.
7.3
Metallic Bonds and Metallic Properties
• A force can change the shape of a metal. A force can
shatter an ionic crystal.
7.2
Formation of Ionic Compounds
•Formation of Ionic
Compounds
–What is the
electrical charge
of an ionic
compound?
•
Compounds
composed of cations and
anions are called ionic
compounds.
•
7.2
Formation of Ionic Compounds
•Formation of Ionic
Compounds
–What is the
electrical charge
of an ionic
compound?
•
Compounds
composed of cations and
anions are called ionic
compounds.
•
Although they are
composed of ions, ionic
compounds are
electrically neutral.
7.2
Formation of Ionic Compounds
• Aluminum metal and
the nonmetal bromine
react to form an ionic
solid, aluminum
bromide.
7.2
Formation of Ionic Compounds
• NaCl is the chemical formula for sodium chloride.
7.2
Properties of Ionic Compounds
–Most ionic compounds are crystalline solids at room
temperature.
–Ionic compounds generally have high melting points.
–Other points to Know?
–Ionic compounds can conduct an electric current
when melted or dissolved in water.
8.1
Molecules and Molecular Compounds
• In nature, matter takes many forms.
The noble gases, including helium and
neon, are monatomic. That means they
exist as single atoms.
• Represented by symbols: He, Ne, etc)
• the noble gases are not molecules
8.1
Molecules and Molecular Compounds
• A molecule is a neutral group of atoms joined together
by covalent bonds. Air contains oxygen molecules.
• A diatomic molecule is a molecule consisting of two
atoms. An oxygen molecule is a diatomic molecule.
8.1
Molecules and Molecular Compounds
Some elements do exist as diatomic molecules.
Hydrogen H2 (g)
Oxygen O2 (g)
Fluorine F2 (g)
Bromine Br2 (l)
Iodine I2 (s)
Nitrogen N2 (g)
Chlorine Cl2 (g)
(note these are molecules but they are not compounds)
8.1
Molecular Formulas
• Formulas of Some Molecular Compounds
Bond Polarity and Polarity of
Molecules
• Bond Polarity can be predicted by differences in
Electronegativity (Use table S)
• Molecules with Polar Bonds may be either polar
or nonpolar
• Use SNAP to predict molecule polarity
• Examples CH4, CO2, H2, are all nonpolar molecules
• (H2O, HCl, NH3 are all polar molecules
8.1
Molecules and Molecular Compounds
8.1
Molecular Formulas
•Chapter 8: Covalent Bonding
Types of
Bonding ?
(review)
Metallic
Bonding
(ch 7)
BONDING
•Sea of electrons model used
to explain bonding in metals
•Kernel & delocalized mobile
valence electrons
Metallic
Bonding
(ch 7)
BONDING
Ionic
Bonding
(ch 7)
Electrostatic attraction of
negatively and positively
charged ions
Can be formed as a result
of the transfer of electrons
between metal and
nonmetal atoms to form
cations and anions
Metallic
Bonding
(ch 7)
BONDING
Ionic
Bonding
(ch 7)
Covalent
Bonding
(ch 8)
• Electrons are shared
between atoms
• Covalent bonds may be
nonpolar (equal sharing of
electrons) or polar
(unequal sharing of
electrons )
8.2
The Octet Rule in Covalent Bonding
•The Octet Rule in Covalent Bonding
–In covalent bonds, electron sharing usually occurs
so that atoms attain the electron configurations of
noble gases.
8.2
Single Covalent Bonds
• The halogens form single covalent bonds in their
diatomic molecules. Fluorine is one example.
8.2
Single Covalent Bonds
• The hydrogen and oxygen atoms attain noble-gas
configurations by sharing electrons.
8.2
Single Covalent Bonds
• The ammonia molecule has one unshared pair of
electrons.
8.2
Single Covalent Bonds
• Methane has no unshared pairs of electrons.
for Conceptual Problem 8.1
Section Assessment
8.2
Double and Triple Covalent Bonds
•Double and Triple Covalent Bonds
– How do atoms form double or triple covalent
bonds?
–Atoms form double or triple covalent bonds if
they can attain a noble gas structure by sharing
two pairs or three pairs of electrons.
8.2
Double and Triple Covalent Bonds
• A bond that involves two shared pairs of electrons is a
double covalent bond. (ex: O2 has a double covalent
bond between the two oxygen atoms)
• A bond formed by sharing three pairs of electrons is a
triple covalent bond. (ex. N2 has a triple covalent bond
between the two nitrogen atoms)
8.2
Double and Triple Covalent Bonds
• O2 molecule: Each oxygen atom has two unshared pair
of electrons. N2 molecule: Each nitrogen has one pair of
unshared electrons
• Lewis dot structure of O2 and N2
8.2
Double and Triple Covalent Bonds
• Carbon dioxide gas is soluble in water and is used to
carbonate many beverages. A carbon dioxide molecule
has two carbon-oxygen double bonds.
8.2
Coordinate Covalent Bonds
• A polyatomic ion, such as NH4+, is a tightly bound group
of atoms that has a positive or negative charge and
behaves as a unit. One of its bonds is a coordinate
covalent bond.
• Most plants need nitrogen that is already combined in a
compound to grow.
Metallic
Bonding
Bonding in:
NaCl ?
HCl ? H2O ?
Bonding in ionic compounds
containing polyatomic ions:
Na2CO3 ?
BaSO4 ? NH4Cl ?
(ch 7)
Ionic
Bonding
(ch 7)
Covalent
Bonding
(ch 8)
9.1
Polyatomic Ions
•Polyatomic Ions
– What are the two endings of the names of most
polyatomic ions?
– (Hint: use Table E)
9.1
Polyatomic Ions
• These models show the structures of four common
polyatomic ions.
9.1
Polyatomic Ions
• Sodium hydrogen carbonate can relieve an upset
stomach.
9.3
Naming Binary Molecular
Compounds
• Carbon and oxygen combine to form carbon monoxide
(CO) and carbon dioxide (CO2), but these two invisible
gases are very different.
Molecular
Compounds
9.3
•A prefix in the name of a binary molecular compound
tells how many atoms of an element are present in
each molecule of the compound.
You MUST know these Prefixes
9.3
Naming Binary Molecular
Compounds
•Some guidelines for naming binary molecular compounds:
»Name the elements in the order listed in the
formula.
»Use prefixes to indicate the number of each
kind of atom.
»Omit the prefix mono- when the formula
contains only one atom of the first element in
the name.
»The suffix of the name of the second element is
-ide.
– 1.
Which of the following compounds is
named INCORRECTLY?
•
•
•
•
CS2, carbon disulfide
BCl3, boron trichloride
IF7, iodine heptafluoride
PCl5, phosphorus hexachloride