Lattice Energy

1
Lattice Energy
2
Properties affected by bond strength

• melting/boiling point (stronger bonds higher
  melting/boiling point)

3
Properties affected by bond strength

• melting/boiling point (stronger bonds higher
  melting point/boiling point)
• hardness (stronger bonds harder crystals)

4
Properties affected by bond strength

• melting/boiling point (stronger bonds higher
  melting point/boiling point)
• hardness (stronger bonds harder crystals)
• odor (stronger bonds weaker odor)

5
Properties affected by bond strength

• melting/boiling point (stronger bonds higher
  melting point/boiling point)
• hardness (stronger bonds harder crystals)
• odor (stronger bonds weaker odor)
• state at room temperature (stronger bonds are
  more likely to be solids)

6
Bond formation

• Whenever a new bond forms, energy is released.
  The stronger the bond, the more energy that is
  released.

7
Bond formation

• Whenever a new bond forms, energy is released.
  The stronger the bond, the more energy that is
  released.
• For ionic bonds, this energy is called lattice
  energy.

8
Bond formation

• Whenever a new bond forms, energy is released.
  The stronger the bond, the more energy that is
  released.
• For ionic bonds, this energy is called lattice
  energy.
• Higher lattice energy values correspond to
  stronger bonds.

9
Bond formation

• Whenever a new bond forms, energy is released.
  The stronger the bond, the more energy that is
  released.
• For ionic bonds, this energy is called lattice
  energy.
• Higher lattice energy values correspond to
  stronger bonds.
• The amount of energy released when a bond forms
  is identical to the amount of energy required to
  break the bond.

10
Predicting lattice energy

• Two factors will determine the lattice energy for
  ionic compounds.

11
Predicting lattice energy

• Two factors will determine the lattice energy for
  ionic compounds.
• Bigger charges produce higher lattice energies
  (2 and 2- produce stronger bonds than 1 and 1-)

12
Predicting lattice energy

• Two factors will determine the lattice energy for
  ionic compounds.
• Bigger charges produce higher lattice energies
  (2 and 2- produce stronger bonds than 1 and 1-)
• Fewer energy levels result in greater lattice
  energies (LiF will have a greater lattice energy
  than NaCl)

13
Predicting lattice energy

• Two factors will determine the lattice energy for
  ionic compounds.
• Bigger charges produce higher lattice energies
  (2 and 2- produce stronger bonds than 1 and 1-)
• Fewer energy levels result in greater lattice
  energies (LiF will have a greater lattice energy
  than NaCl)
• Charge is by far the bigger factor and should
  always be compared first!!!

14
Which compound will have the greatest lattice
energy, MgS or LiF?
15
Which compound will have the greatest lattice
energy, MgS or LiF?

• Magnitude of charge is the first thing we should
  look at.

16
Which compound will have the greatest lattice
energy, MgS or LiF?

• Magnitude of charge is the first thing we should
  look at.
• magnesium (2 charge), sulfide (2- charge)

17
Which compound will have the greatest lattice
energy, MgS or LiF?

• Magnitude of charge is the first thing we should
  look at.
• magnesium (2 charge), sulfide (2- charge)
• lithium (1 charge), fluoride (1- charge)

18
Which compound will have the greatest lattice
energy, MgS or LiF?

• Magnitude of charge is the first thing we should
  look at.
• magnesium (2 charge), sulfide (2- charge)
• lithium (1 charge), fluoride (1- charge)
• MgS has the greater individual charges, so MgS
  has the greater lattice energy.

19
Which compound will have a lower melting point,
Na2S or BeO?
20
Which compound will have a lower melting point,
Na2S or BeO?

• A lower melting point means we need to select the
  compound with the lower lattice energy. We check
  the charges first.

21
Which compound will have a lower melting point,
Na2S or BeO?

• A lower melting point means we need to select the
  compound with the lower lattice energy. We check
  the charges first.
• sodium (1), sulfide (2-)

22
Which compound will have a lower melting point,
Na2S or BeO?

• A lower melting point means we need to select the
  compound with the lower lattice energy. We check
  the charges first.
• sodium (1), sulfide (2-)
• beryllium (2), oxide (2-)

23
Which compound will have a lower melting point,
Na2S or BeO?

• A lower melting point means we need to select the
  compound with the lower lattice energy. We check
  the charges first.
• sodium (1), sulfide (2-)
• beryllium (2), oxide (2-)
• sodium sulfide has smaller individual charges, so
  it has the lower melting point.

24
Which compound has harder crystals, CaCl2 or
MgCl2?
25
Which compound has harder crystals, CaCl2 or
MgCl2?

• Harder crystals require a higher lattice energy.
  First, check the charges.

26
Which compound has harder crystals, CaCl2 or
MgCl2?

• Harder crystals require a higher lattice energy.
  First, check the charges.
• calcium (2), chloride (1-)

27
Which compound has harder crystals, CaCl2 or
MgCl2?

• Harder crystals require a higher lattice energy.
  First, check the charges.
• calcium (2), chloride (1-)
• magnesium (2), chloride (1-)

28
Which compound has harder crystals, CaCl2 or
MgCl2?

• Harder crystals require a higher lattice energy.
  First, check the charges.
• calcium (2), chloride (1-)
• magnesium (2), chloride (1-)
• the charges are the same, so we need to see which
  ions have fewer energy levels.

29
Which compound has harder crystals, CaCl2 or
MgCl2?

• the charges are the same, so we need to see which
  ions have fewer energy levels.
• calcium (4), chloride (3)

30
Which compound has harder crystals, CaCl2 or
MgCl2?

• the charges are the same, so we need to see which
  ions have fewer energy levels.
• calcium (4), chloride (3)
• magnesium (3), chloride (3)

31
Which compound has harder crystals, CaCl2 or
MgCl2?

• the charges are the same, so we need to see which
  ions have fewer energy levels.
• calcium (4), chloride (3)
• magnesium (3), chloride (3)
• fewer energy levels give MgCl2 the higher lattice
  energy and therefore, the harder crystals.

32
Which compound has the lower boiling point, AgNO3
or K2SO4?
33
Which compound has the lower boiling point, AgNO3
or K2SO4?

• Lower boiling point means a lower lattice energy.

34
Which compound has the lower boiling point, AgNO3
or K2SO4?

• Lower boiling point means a lower lattice energy.
• silver (1), nitrate (1-)

35
Which compound has the lower boiling point, AgNO3
or K2SO4?

• Lower boiling point means a lower lattice energy.
• silver (1), nitrate (1-)
• potassium (1), sulfate (2-)

36
Which compound has the lower boiling point, AgNO3
or K2SO4?

• Lower boiling point means a lower lattice energy.
• silver (1), nitrate (1-)
• potassium (1), sulfate (2-)
• Charges indicate a lower lattice energy for
  AgNO3. Lower lattice energy means a lower
  boiling point.