• Atomic Hook-ups:
Types of Chemical
Bonds
Properties of Ionic Compounds
• Crystalline structure.
• A regular repeating
arrangement of ions in the solid.
• Ions are strongly bonded.
– Ionic Bond: the chemical bond from
electrostatic attraction between
positive & negative charges
– EN Difference > 1.67 (see p. 266)
Crystalline structure
The
POSITIVE
CATIONS
stick to the
NEGATIVE
ANIONS, like
a magnet.
+
+
- - +
+ + - + - +
- + - +
Properties of Ionic Compounds
• Structure is rigid.
• High melting points- because of
strong forces between ions.
Do they Conduct?
• Conducting electricity is allowing
charges to move.
• In a solid, the ions are locked in place.
• Ionic solids are insulators.
• When melted, the ions can move
around.
• Melted ionic compounds conduct.
• First get them to 800ºC.
• Dissolved in water they conduct.
Ionic solids are brittle
+
+
-
+
+
+
+
-
+
+
Ionic solids are brittle
• Strong Repulsion breaks crystal apart.
- + - +
+ - + - + - +
Properties of Ionic Compounds
(cont.)
Section 7-2
• This figure demonstrates how and why
crystals break when an external force is
applied.
Metallic Bonds
• How atoms are held together in
the solid.
• Metals hold onto their valence
electrons very weakly.
• Think of them as positive ions
floating in a “sea” of electrons.
Sea of Electrons
• Electrons are free to move through the
solid.
• Metals conduct electricity.
+
+ + +
+ + + +
+ + + +
Metallic Bonds and the Properties of Metals
(cont.)
• A metallic bond is the attraction of a
metallic cation for delocalized electrons.
Bozeman Science – Metallic Bond
http://www.youtube.com/watch?v=c4udBSZfLHY
http://www.youtube.com/watch?v=Bjf9gMDP47s
Metals are Malleable
• Hammered into shape
(bend).
• Ductile - drawn into
wires.
Malleable
+
+ + +
+ + + +
+ + + +
Malleable
• Electrons allow atoms to slide by.
+ + + +
+ + + +
+ + + +
Metallic Bonds and the Properties of Metals
(cont.)
• Metals are malleable because they can be
hammered into sheets.
• Metals are ductile because they can be
drawn into wires.
http://www.youtube.com/watch?v=OkuDM3hYutI&NR=1
Metal Alloys
• An alloy is a mixture of elements that has
metallic properties.
• The properties of alloys differ from the
elements they contain.
Metal Alloys (cont.)
Metal Alloys (cont.)
• Substitutional alloys are formed when
some atoms in the original metallic solid
are replaced by other metals of similar
atomic structure.
• Interstitial alloys are formed when small
holes in a metallic crystal are filled with
smaller atoms.
COVALENT BONDING
When an atom of one
nonmetal
shares one or more
electrons
with an atom of another
nonmetal so both atoms
end up with
eight valence electrons
COVALENT BOND
FORMATION
When one nonmetal shares one or
more electrons with an atom of
another nonmetal so both atoms end
up with eight valence electrons
COVALENT BONDING
IS THE COMPOUND
A COVALENT COMPOUND?
NONMETAL
NONMETAL
YES since it is made of only nonmetal elements
Characteristics of Covalent
Bonding
• Low Melting Point
• Brittle
• Do NOT conduct electricity
Covalent bonding
• Fluorine has seven valence electrons
F
Covalent bonding
• Fluorine has seven valence electrons
• A second atom also has seven
F
F
Covalent bonding
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons
F
F
Covalent bonding
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons
F
F
Covalent bonding
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons
F F
Covalent bonding
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons
F F
Covalent bonding
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons
F F
Covalent bonding
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons
Both end with full orbitals
F F
Covalent bonding
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons
Both end with full orbitals
F F
8 Valence
electrons
Covalent bonding
Fluorine has seven valence electrons
A second atom also has seven
By sharing electrons
Both end with full orbitals
8 Valence
electrons
F F