Ionic Bonding
Formation of Bond
Electrons are transferred from an atom of
low electronegativity to one of high
electronegativity
 Anion (-) and cation (+) formed
 Opposite charges attract – called an
electrostatic force

Formula Unit
Simplest ratio of atoms in an ionic
compound
 Charges combine to form a net of zero
 Formulas are not molecules: they do not
show exact numbers of atoms just ratios
 Another term for an ionic compound is salt

Example

Show how the bond forms in each pair and
tell the formula unit
Ca and F
K and O
Al and O
Ions Arrangement
Opposite ions arrange themselves with
each positive ion surrounded by negative
ions and each negative surrounded by
positive ions
 Where potential energy is lowest
 This arrangement is called a crystal lattice

Lattice Energy
Energy released when one mole of an
ionic compound is formed from its ions
 Values will always be negative, because
energy is released
 The larger the negative value for the lattice
energy, the stronger the ionic bond in the
crystal is

Lattice energy
Compound
NaCl
NaBr
CaF2
CaO
LiCl
LiF
MgO
KCl
(kJ/mol)
−787.5
−751.4
−2634.7
−3385
−861.3
−1032
−3760
−715
The notation for sodium
chloride, NaCl, stands for one .
A)
B)
C)
D)
Formula unit
Molecule
Crystal
Atom
In a crystal of an ionic compound, each
cation is surrounded by a number of .
A)
B)
C)
D)
Molecules
Positive ions
Dipoles
Negative ions
Compared with the neutral atoms involved
in the formation of an ionic compound, the
crystal lattice that results is .
A)
B)
C)
D)
Higher in potential energy
Lower in potential energy
Equal in potential energy
Unstable
The lattice energy of compound A is greater
than that of compound B. What can be
concluded from this fact?
A)
B)
C)
D)
Compound A is not an ionic compound
It will be more difficult to break the
bonds in compound A than in
compound B
Compound B is probably a gas
Compound A has larger crystals than
compound B
The forces of attraction between
molecules in a molecular compound
are .
A)
B)
C)
D)
Stronger than the attractive forces in ionic
bonding
Weaker than the attractive forces in ionic
bonding
Approximately equal to the attractive
forces in ionic bonding
Equal to zero
What type of force holds atoms
together in an ionic bond?
A)
B)
C)
D)
Van der Waals
Dipole-dipole
Electrostatic
Hydrogen bonding
What type of bonding holds a
polyatomic ion together?
A)
B)
C)
D)
Ionic
Metallic
Covalent
Hydrogen Bonding
Using the table below, which substance is
held together by the strongest ionic bond?
A)
B)
C)
D)
E)
NaCl
CaO
KCl
MgO
LiCl