Chemical Bonding
IONIC BONDS
NOV. 21
Ionic Bonds
Characterized by a transfer of electrons
 When electrons are transferred between
atoms ions are produced having opposite
charges
The attraction of oppositely charged ions
holds them together
This electrostatic attraction is the ionic
bond

Ionic Bonds- Example
An example of a substance having ionic
bonds is NaCl, sodium chloride. (Watch the
bond being formed in the demonstration
below)
Na Na Cl
Cl
Ionic Bonds - Forming NaCl
Sodium is in Group 1, so it has one
valence electron 1s22s2 2p6 3s1
 Chlorine is in Group 17 and has seven
valence electrons 1s22s2 2p63s23p5
Ionic Bonds - Forming NaCl
The valence electrons of the Na and Cl atoms
rearrange to give each atom a noble gas
configuration of valence electrons
 If the one valence electron of sodium is
transferred to the chlorine atom, chlorine becomes
stable with an octet of electrons.
1s22s2 2p63s23p6
 The sodium also becomes stable because it’s outer
energy level is now the 2nd with eight electrons.
1s22s2 2p6
Ionic Bonds - Forming NaCl
 Because the chlorine atom now has an extra
electron, it has a negative charge
Negatively charged ions are called anions
 Because sodium lost an electron, it now has an
unbalanced proton in the nucleus and therefore
has a positive charge
 Positively charged ions are called cations
The charge on an ion is called its oxidation
number or oxidation state
Ionic Bonds - Forming NaCl
A compound that is composed of
ions is called an ionic compound
Note that only the arrangement of
electrons has changed
Nothing about the atom’s nucleus has
changed
Check for Understanding
1.Write out the configuration for a
magnesium ion. 1s2 2s2 2p6 (the same as Ne)
2. Predict the charge on a magnesium
ion. Mg +2
3. How many electrons has it lost? 2 e4. Write out the electron configuration
for a Sulfur ion. 1s2 2s2 2p6 3s2 3p6
5. Predict the charge on a sulfur ion. S -2
6. How many electrons has it gained? 2 e7. What would the resulting compound
look like? MgS
Characteristics of Ionic Compounds:
High melting points
 Conduct electricity in the liquid & gaseous
states
 Considered electrolytes: soluble in water
and conduct electricity when dissolved in
water
 Usually crystallize as sharply defined
particles
 They are typically composed of a metal and
a nonmetal

Crystal Structure of Ionic Compound
Composed of well-organized, tightly bound ions
Form strong, three-dimensional crystal structure
Crystalline solids at room temperature
Positive ions are surrounded by negative ions,
and negative ions by positive ions
Resulting structure is called a crystal lattice and
contains a regular, repeating, three-dimensional
arrangement of ions
Lattice Energy
Energy
required to separate one mole of
the ions of an ionic compound and is
expressed as a negative quantity
The
greater (that is, the more negative) the
lattice energy is, the stronger the force of
attraction between ions
Lattice energy tends to be greater for morehighly-charged ions and for small ions than
for ions of lower charge or large size
Check for Understanding
1. What is involved in an ionic bond?
2. What are the types of particles formed?
3. What actually is the ionic bond?
4. Give two characteristics of ionic
compounds.
5. What two classes of elements are ionic
compounds usually composed of?
6. Describe the arrangement of particles
in an ionic crystal and what is the
resulting structure called
1. TRANSFER OF ELECTRONS
2. IONS
3. ELECTROSTATIC ATTRACTION
4. HIGH MELTING PTS, CRYSTALLINE
STRUCTURE
5. METAL AND NONMETAL
6. HIGHLY ORGANIZED CRYSTALLINE
LATTICE