Section 8.4
Metallic Bonds and
Properties of Metals
Objectives
 Describe
a metallic bond
 Explain the physical properties of
metals in terms of metallic bonds
 Define and describe alloys
Key Terms
 Electron
sea model
 Delocalized electrons
 Metallic bond
 Alloy
Metallic Bonds
 Metals
do not bond ionically with
other metals
 Metals form a crystal lattice
similar to an ionic compound.
 In the lattice the outer energy
levels of the atoms overlap
Electron Sea Model
 All
the metal atoms in a
metallic solid contribute their
valence electrons to form a ‘sea’
of electrons
Delocalized Electrons
 These
valence electrons are not
held by a specific atom and can
move freely from atom to atom
Metallic Bond
 Metals
with wandering electrons
become cations
 The cations are attracted to the
other atom’s delocalized electrons
 This attraction is called a
metallic bond
Properties of Metals
Metals are good conductors of heat
or electricity
 The delocalized electrons in a metal
easily carry the heat or electricity
through the metal
 The delocalized electrons in metals
also absorb and release electrons
when exposed to light, giving metals
their shiny luster.

Metal Alloys
 An
alloy is a mixture of elements
that have metallic properties
 Because of the nature of the
metallic bond it is relatively
easy to introduce other
elements into the metallic
crystal
2 Types of Metal Alloys
1. Substitutional alloy -replaces metal
atoms with atoms of similar size
Ex: copper atoms replace silver
atoms in sterling silver
2. Interstitial alloy -fills in the gaps
between metal atoms with smaller
atoms
Ex: carbon atoms fill in the gaps
between iron atoms in carbon steel
Homework
P.
231 #40-45
P.237 #80-82,84