Callister - An introduction - 8th edition

Summary • 39
Primary Interatomic Bonds
• For ionic bonds, electrically charged ions are formed by the transference of valence
electrons from one atom type to another. This type of bonding is found in
ceramic materials.
• There is a sharing of valence electrons between adjacent atoms when bonding is
covalent. Polymers and some ceramic materials covalently bond.
• The percent ionic character (%IC) of a bond between two elements (A and B)
depends on their electronegativities (X’s) according to Equation 2.10.
• With metallic bonding, the valence electrons form a “sea of electrons” that is uniformly
dispersed around the metal ion cores and acts as a form of glue for them.
Metallic materials exhibit this type of bonding.
Secondary Bonding or van der Waals Bonding
• Relatively weak van der Waals bonds result from attractive forces between electric
dipoles, which may be induced or permanent.
• For hydrogen bonding, highly polar molecules form when hydrogen covalently
bonds to a nonmetallic element such as fluorine.
Equation Summary
Equation
Page
Number Equation Solving for Number
2.4
E F dr
Potential energy between
two atoms
29
2.8
E A A r
Attractive energy between
two atoms
31
2.9
E R B r n
Repulsive energy between
two atoms
31
2
2.10 %IC e 1 exp c 10.252 aX A X B b df 100 Percent ionic character 33
List of Symbols
Symbol
Meaning
A, B, n Material constants
E
Potential energy between two atoms/ions
E A
Attractive energy between two atoms/ions
E R
Repulsive energy between two atoms/ions
F
Force between two atoms/ions
r
Separation distance between two atoms/ions
X A
Electronegativity value of the more electronegative
element for compound BA
X B
Electronegativity value of the more electropositive
element for compound BA