1. GIANT IONIC LATTICES

2. Very strong electrostatic attraction
Ionic Bonding
- the net electrostatic attractions between oppositely charged ions - +
Cation
Anion
Very strong electrostatic attraction

3. How are ions formed? By atoms losing or gaining electrons
More electronegative non-metal atoms GAIN electrons FROM metal atoms
CATIONS (+) are formed when atoms (USUALLY METALS) lose electrons to non-metal
ANIONS (-) are formed when atoms (USUALLY NON-METALS) gain electrons from metal
Example
Example
Na - 1s22s22p63s1
F - 1s22s22p5
loses its 3s electron to form
gains an electron to form
Na+ - 1s22s22p63s0
F- - 1s22s22p6
Ions are isoelectronic with nearest noble gas

4. Na+Cl-(s) IONIC BONDING IN SODIUM CHLORIDE
Showing only outer energy levels: Na X
2 , 8 , 1 Cl X
2 , 8 , 7
Na+
2 , 8
Cl- X
2 , 8 , 8
3D giant lattice with 1:1 ratio of ions to give electrical neutrality
Na+Cl-(s)

5. General Ionic Structure
ions arrange in a giant lattice structure
cations and anions arranged alternately
3-dimensional array
lattice is very strong due to many ionic bonds

6. Sodium chloride crystal lattice
GIANT IONIC CRYSTAL LATTICE
Oppositely charged ions held in a regular
3-dimensional lattice by electrostatic attraction
The arrangement of ions in a crystal lattice depends on the relative sizes of the ions
Sodium chloride crystal lattice
Cl-
Chloride ion
Na+
Sodium ion
The Na+ ion is small enough relative to a Cl¯ ion to fit in the spaces so that both ions occur in every plane.

7. Sodium chloride crystal lattice
GIANT IONIC CRYSTAL LATTICE
Oppositely charged ions held in a regular
3-dimensional lattice by electrostatic attraction
The arrangement of ions in a crystal lattice depends on the relative sizes of the ions
Sodium chloride crystal lattice
Each Na+ is surrounded by 6 Cl¯ (co-ordination number = 6)
and each Cl¯ is surrounded by 6 Na+ (co-ordination number = 6).

8. Sodium chloride crystal lattice
GIANT IONIC CRYSTAL LATTICE
Oppositely charged ions held in a regular
3-dimensional lattice by electrostatic attraction
The arrangement of ions in a crystal lattice depends on the relative sizes of the ions
Sodium chloride crystal lattice
Each Na+ is surrounded by 6 Cl¯ (co-ordination number = 6)
and each Cl¯ is surrounded by 6 Na+ (co-ordination number = 6).

9. Summary - The Sodium Chloride Lattice
= Na+
= Cl-
Each Na+ ion is surrounded by six Cl- ions
Each Cl- ion is surrounded by six Na+ ions
 6:6 coordination
 Na1Cl1 formula
Face Centred Cubic Structure

10. Caesium chloride crystal lattice
GIANT IONIC CRYSTAL LATTICE
Oppositely charged ions held in a regular
3-dimensional lattice by electrostatic attraction
The arrangement of ions in a crystal lattice depends on the relative sizes of the ions
Caesium chloride crystal lattice
Each Cs+ is surrounded by 8 Cl¯ (co-ordination number = 8)
and each Cl¯ is surrounded by 8 Cs+ (co-ordination number = 8).

11. Caesium chloride crystal lattice
GIANT IONIC CRYSTAL LATTICE
Oppositely charged ions held in a regular
3-dimensional lattice by electrostatic attraction
The arrangement of ions in a crystal lattice depends on the relative sizes of the ions
Caesium chloride crystal lattice
Each Cs+ is surrounded by 8 Cl¯ (co-ordination number = 8)
and each Cl¯ is surrounded by 8 Cs+ (co-ordination number = 8).

12. Summary - The Caesium Chloride Lattice
= Na+
= Cl-
Each Cs+ ion is surrounded by eight Cl- ions
Each Cl- ion is surrounded by eight Cs+ ions
8 :8 coordination
 Cs1Cl1 formula
Body Centred Cubic Structure

13. A comparison of the sodium chloride and caesium chloride lattices
Type of structure
Face Centred Cubic
Body
Centred Cubic
Coordination
number
6:6
8:8
The structures of NaCl and CsCl are different because the Cs+ ion is larger than the Na+ ion, and is therefore able to surround itself with 8Cl-ions, whereas the Na+ ion is smaller and can only fit 6Cl- ions around itself

14. Physical properties of ionic compounds
Melting point
very high A large amount of energy must be put in to overcome the
strong electrostatic attractions and separate the ions.
Strength
Very brittle Any dislocation leads to the layers moving and similarly charged
ions being next to each other. The repulsion splits the crystal.
Electrical do not conduct when solid - ions are held strongly in the lattice.
conduct when molten or in aqueous solution - the ions become
mobile and conduction takes place.
Solubility Insoluble in non-polar solvents but soluble in water
Water as it is a polar solvent and stabilises the separated ions.
Much energy is needed to overcome the electrostatic attraction and separate the ions
stability attained by being surrounded by polar water molecules compensates for this

15. BRITTLE IONIC LATTICES
IONIC BONDING
BRITTLE IONIC LATTICES + -
IF YOU MOVE A LAYER OF IONS, YOU GET IONS OF THE SAME CHARGE NEXT TO EACH OTHER. THE LAYERS REPEL EACH OTHER AND THE CRYSTAL BREAKS UP.