Download Properties That Reflect Metallic Bonding - Kasson

Chapter
8
Ionic Compounds
• Chemical Bond – the force that holds
atoms together
• Cations are + electrons are lost
• Anions are electrons are gained
Ionic bond
• The electrostatic force that holds
oppositely charged particles together is
referred to as an ionic bond
• It is a strong bond
• Results in crystal formation, high melting
points, compounds are hard, rigid, and
brittle.
• An ionic compound whose aqueous
solution conducts electricity is called an
electrolyte
• Ionic Solids are not conductors
• Conductors when Molten or Dissolved
Lattice energy
• The energy released when one mole of
the ions of an ionic compound come
together is referred to as the lattice energy
• related to size of the ions
• Also affected by charge
• See table 8.3 page 220
• Formula unit
• Monatomic ion
• Oxidation number – the apparent charge
on an atom
• Polyatomic ion – see table 8-6 page 224
• Oxyanion contains oxygen
Chemical Bonding: Basic Concepts
Topic
11
Properties That Reflect
Metallic Bonding
• Metals and alloys are malleable and ductile,
and they conduct electricity.
• When a metal can be pounded
or rolled into thin sheets, it is
called malleable.
Chemical Bonding: Basic Concepts
Topic
11
Properties That Reflect
Metallic Bonding
• Ductile metals can be drawn into wires.
• For example, copper can be pulled into thin
strands of wire and used in electric circuits.
Chemical Bonding: Basic Concepts
Topic
11
Properties That Reflect
Metallic Bonding
• Electrical conductivity is a measure of how
easily electrons can flow through a material
to produce an electric current.
• These properties —malleability, ductility, and
electrical conductivity—are the result of the
way that metal atoms bond with each other.
Chemical Bonding: Basic Concepts
Topic
11
Sea of Valence Electrons
• The valence electrons of metal atoms are
loosely held by the positively charged
nucleus.
• Sometimes, metal atoms form ionic bonds
with non-metals by losing one or more of
their valence electrons and forming
positive ions.
• However, in metallic bonding, metal atoms
don't lose their valence electrons.
Chemical Bonding: Basic Concepts
Topic
11
Sea of Valence Electrons
• Metal atoms release their valence electrons
into a sea of electrons shared by all of the
metal atoms. The bond that results from
this shared pool of valence electrons is
called a metallic bond.
Chemical Bonding: Basic Concepts
Topic
11
Atomic View of Metallic Bonding
• Each atom in
this model of a
Group 2 metal
releases its two
valence electrons
into a pool of
electrons to be
shared by all of
the metal atoms.
Chemical Bonding: Basic Concepts
Topic
11
Atomic View of Metallic Bonding
• Bonding in metals is
not rigid.
• As a metal is struck
by a hammer, the
atoms slide through
the electron sea to
new positions while continuing to maintain
their connections to each other.
• The same ability to reorganize explains why
metals can be pulled into long, thin wires.
Alloys
• Substitutional
• example is sterling silver
• Interstitial
• Example is carbon steel