1. Formation of Ionic compounds
Born Haber cycles
Formation of Ionic compounds

2. Formation of MX (Cation = +1, Anion = -1)
Write a balanced equation for the formation
M(s) + ½ X2(g)  MX(s) (eg Na(s) + ½ Cl2(g)  NaCl(s) if NaCl)
What bond is present in this compound?
Ionic Bond
What ions are present in this compound?
M+ and X- (eg Na+ and Cl- if NaCl)
How is the bond formed?
Attraction between M+ and X- as they move together M + X -
ie M+(g) + X-(g)  MX(s)

3. What has to happen while MX forms?
M(s) + ½ X2(g)  MX(s) and M +(g) + X -(g)  MX(s)
What processes occur during the formation of MX?
M(s)  M(g)
½ X2(g) X(g)
M(g)  M+(g) + e-
X(g) + e-  X-(g)
M +(g) + X -(g)  MX(s)
Which of these are exothermic and which are endothemic?
What are the names of these processes?
Endo (have to break metallic bond)
Endo (have to break covalent bond
Endo (have to overcome attraction between nucleus and electrons)
Exo (electrons attracted to the nucleus)
Exo (ions attract)
A , B: Atomisation ( H(at) : The enthalpy change associated with the formation of one mole of gaseous atoms
C : 1st Ionisation energy: The amount of energy required to remove one of electrons from one mole of gaseous atoms
D : 1st Electron Affinity: The amount of energy given out when one mole of gaseous atoms gains one mole of electrons
E : Lattice energy: The enthalpy change associated with the formation of one mole of an ionic lattice from its gaseous ions

4. Formation of MX (Cation = +2, Anion = -2)
Write a balanced equation for the formation
M(s) + ½ X2(g)  MX(s) (eg Mg(s) + ½ O2(g)  MgO(s) if MgO)
What bond is present in this compound?
Ionic Bond
What ions are present in this compound?
M+2 and X-2 (eg Mg+2 and O-2 if MgO)
How is the bond formed?
Attraction between M+2 and X-2 as they move together M +2 X -2
ie M+2(g) + X-2(g)  MX(s)

5. What has to happen while MX forms?
M(s) + ½ X2(g)  MX(s) and M +2(g) + X -2(g)  MX(s)
What processes occur during the formation of MX?
M(s)  M(g)
½ X2(g) X(g)
M(g)  M+(g) + e-
M+(g)  M+2 + e-
X(g) + e-  X-(g)
X-(g) + e-  X-2(g)
M +2(g) + X -2(g)  MX(s)
Which of these are exothermic and which are endothemic?
What are the names of these processes?
Endo (have to break metallic bond)
Endo (have to break covalent bond
Endo (have to overcome attraction between nucleus and electrons)
Exo (electrons attracted to the nucleus)
Endo (electrons are repelled by the negative charge)
Exo (ions attract)
A , B: Atomisation ( H(at) : The enthalpy change associated with the formation of one mole of gaseous atoms
C : 1st Ionisation energy: The amount of energy required to remove one of electrons from one mole of gaseous atoms
D : 2nd Ionisation energy: The amount of energy required to remove one of electrons from one mole of gaseous ions
E : 1st Electron Affinity: The amount of energy given out when one mole of gaseous atoms gains one mole of electrons
F :2nd Electron Affinity: The amount of energy required for one mole of gaseous atoms to gain one mole of electrons
G : Lattice energy: The enthalpy change associated with the formation of one mole of an ionic lattice from its gaseous ions

6. Formation of MX2 (Cation = +2, Anion = -1)
Write a balanced equation for the formation
M(s) + X2(g)  MX2(s) (eg Mg(s) + F2(g)  MgF2(s) if MgF2)
What bond is present in this compound?
Ionic Bond
What ions are present in this compound?
M+2 and X- (eg Mg+2 and F- if MgF2)
How is the bond formed?
Attraction between M+2 and X- as they move together X - M +2 X -
ie M+2(g) + 2X-(g)  MX2(s)

7. What has to happen while MX forms?
M(s) + X2(g)  MX(s) and M +2(g)+ 2X - (g)  MX2 (s)
What processes occur during the formation of MX?
M(s)  M(g)
X2(g) 2X(g)
M(g)  M+(g) + e-
M+(g)  M+2 + e-
2X(g) + 2e-  2X-(g)
M +2(g) + 2X -(g)  MX2(s)
Which of these are exothermic and which are endothemic?
What are the names of these processes?
Endo (have to break metallic bond)
Endo (have to break covalent bond
Endo (have to overcome attraction between nucleus and electrons)
Exo (electrons attracted to the nucleus)
Exo (ions attract)
A : Atomisation ( H(at) : The enthalpy change associated with the formation of one mole of gaseous atoms
B : Atomisation (2 x H(at) : The enthalpy change associated with the formation of one mole of gaseous atoms
C : 1st Ionisation energy: The amount of energy required to remove one of electrons from one mole of gaseous atoms
D : 2nd Ionisation energy: The amount of energy required to remove one of electrons from one mole of gaseous ions
E : 2 x 1st Electron Affinity: The amount of energy given out when one mole of gaseous atoms gains one mole of electrons
G : Lattice energy: The enthalpy change associated with the formation of one mole of an ionic lattice from its gaseous ions

8. Formation of M2X (Cation = +1, Anion = -2)
Write a balanced equation for the formation
2M(s) + ½X2(g)  M2X(s) (eg 2Na(s) + ½O2(g)  Na2O(s) if Na2O)
What bond is present in this compound?
Ionic Bond
What ions are present in this compound?
M+2 and X- (eg Na+ and O-2 if Na2O)
How is the bond formed?
Attraction between M+ and X-2 as they move together M + X - M +
ie M+ (g) + X-2(g)  M2O (s)

9. What has to happen while M2X forms?
2M(s) + ½ X2(g)  M2X(s) and 2M + (g) + X -2 (g)  M2X (s)
What processes occur during the formation of MX?
2M(s)  2M(g)
X2(g) 2X(g)
2M(g)  2M+(g) + 2e-
X(g) + e-  X-(g)
2X(g) + 2e-  2X-(g)
2M +(g) + X -2(g)  M2X(s)
Which of these are exothermic and which are endothemic?
What are the names of these processes?
Endo (have to break metallic bond)
Endo (have to break covalent bond
Endo (have to overcome attraction between nucleus and e-
Exo (electrons attracted to the nucleus)
Endo (have to overcome repulsion between negative ion and e-
Exo (ions attract)
A : Atomisation ( H(at) : The enthalpy change associated with the formation of one mole of gaseous atoms
B : Atomisation ( H(at) : The enthalpy change associated with the formation of one mole of gaseous atoms
C :2x 1st Ionisation energy: The amount of energy required to remove one of electrons from one mole of gaseous atoms
E : 1st Electron Affinity: The amount of energy given out when one mole of gaseous atoms gains one mole of electrons
F : 2nd Electron Affinity: The amount of energy required for one mole of gaseous atoms to gain one mole of electrons
G : Lattice energy: The enthalpy change associated with the formation of one mole of an ionic lattice from its gaseous ions

10. Draw Born Haber cycle MX (+/-)

11. Draw Born Haber cycle MX (+2/-2)

12. Draw Born Haber cycle MX2 (+2/-1)

13. Draw Born Haber cycle M2X (+1/-2)

14. Solubility Definitions
Enthalpy of Solution: Eg
NaCl(s)  Na+(aq) + Cl-(aq)
CuSO4(s)  Cu2+(aq) + SO4-2(aq)
MgCl2(s)  Mg2+(aq) + 2Cl-(aq)
Hydration Energy:
Na+(g)  Na+(aq)
Cl-(g)  Cl-(aq)
Cu2+(g)  Cu2+(aq)
SO4-2(g)  SO4-2(aq)
Mg2+(g)  Mg2+(aq)
2Cl-(g)  2Cl-(aq) (2HHE Cl-)
The enthalpy change associated with the dissolving of ONE MOLE of an IONIC compound in water
The enthalpy change associated with hydration of ONE mole of Gaseous ions
There are 6 molecules of water around each ion
What makes an ion have a Highly Exothermic Hydration Energy?
SMALL and HIGHLY CHARGED

15. What happens when a solid dissolves?If
NaCl(s)  Na+(aq) + Cl-(aq)
Then the following has to happen
NaCl(s)  Na+(g) + Cl-(g) The lattice has to be broken up (supply the LE)
Na+(g) + Cl-(g)  Na+(aq) + Cl-(aq) The ions are hydrated (Hydration energy is given out)
Hence we can set up a Hess Cycle
Hsoln NaCl
HHE(Na) +
HLENaCl
HHE(Cl)
HENCE
HLENaCl + Hsoln NaCl = HHE(Na) + HHE(Cl)

16. What happens when a solid dissolves?If
MgCl2(s)  Mg+2(aq) + 2Cl-(aq)
Then the following has to happen
MgCl2(s)  Mg+2(g) + 2Cl-(g) The lattice has to be broken up (supply the LE)
Mg+2(g) + 2Cl-(g)  Mg+2(aq) + 2Cl-(aq) The ions are hydrated (Hydration energy is given out)
Hence we can set up a Hess Cycle
Hsoln MgCl 2
HHE(Mg)
HLEMgCl
2HHE(Cl) 2 +
HENCE
HLEMgCl + Hsoln MgCl = HHE(Mg) + 2HHE(Cl) 2 2

17. Problems with Born Haber Cycle
Assumes TRUE IONIC BONDING
No Polarisation occurs
This is only true for ionic compounds formed between:
LARGE CATION
LOWLY CHARGED CATION
SMALL ANIONS

18. Polarised Ionic Small Highly charged cation
(Nucleus of cation is not shielded greatly)
Large anion
Outer shell of anion is shielded from its’ nucleus
RESULT:
Outer shell of anion is attracted towards the nucleus of the cation
Distorts (polarises) the shape of the anion

19. Polarised ionic 9 - 3 +
LiF: F Outershell electrons pulled towards F nucleus- so NO Distortion 9 - 9 - 3 +
LiI: I Outershell electrons pulled towards Li nucleus- so Distortion occurs (Polarised Ionic)