1. IB Chemistry Power Points
Topic 4
Bonding
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LECTURE 1
Ionic Bonding

3. STRUCTURE AND BONDING
Key Concept:
The physical properties of a substance (such as hardness, density, melting
point and conductivity) depend on the structure of the substance. Bonding
determines arrangement of particles and therefore, the type of structure.
Basic theory – things you should know
1. The noble gases (He, Ne, Ar, Kr, Xe and Rn) are in Group VIII, they are all
relatively inert meaning they do not react and bond like other elements.
2. We can conclude that noble gas electron configuration appears to confer
stability. All noble gases have just filled their ‗outer shell‘ of electrons
3. Other elements have a tendency to obtain the same electron arrangement
(a full outer shell of valence electrons). Obtaining this electron
arrangement is accomplished by different methods of chemical bonding.
4. The type of bonding depends on an element‘s position in the periodic
table

4. TYPES OF BONDING
CHEMICAL BONDS....
are strong intramolecular bonds that hold atoms
together in molecules, ionic solids and metals. These
bonds are broken and made in chemical reactions.
ionic
covalent
dative covalent (or co-ordinate)
metallic
PHYSICAL BONDS....
are intermolecular forces that exist between two or
more separate molecules. These are the attractions
involved in physical changes.
van der Waals‗ forces - weakest
dipole-dipole interactions
hydrogen bonds - strongest

5. PART 1: CHEMICAL BONDS

6. THE IONIC BOND
Ionic bonds are formed between elements whose atoms tend to ―lose‖
electrons to gain the nearest noble gas electronic configuration and those
which tend to ―gain‖ electrons. The electrons are transferred from one atom to
the other.
Sodium Chloride
+
Na ——> Na + e¯ and Cl + e¯ ——> Cl¯

7. THE IONIC BOND
Ionic bonds are formed between elements whose atoms tend to ―lose‖
electrons to gain the nearest noble gas electronic configuration and those
which tend to ―gain‖ electrons. The electrons are transferred from one atom to
the other.
Sodium Chloride
+
Na ——> Na + e¯ and Cl + e¯ ——> Cl¯
2,8,1 2,8 2,8,7 2,8,8

8. THE IONIC BOND
Ionic bonds are formed between elements whose atoms tend to ―lose‖
electrons to gain the nearest noble gas electronic configuration and those
which tend to ―gain‖ electrons. The electrons are transferred from one atom to
the other.
Sodium Chloride
+
Na ——> Na + e¯ and Cl + e¯ ——> Cl¯
2,8,1 2,8 2,8,7 2,8,8
2 2 6 1 2 2 6 2 2 6 2 5 2 2 6 2 6
or 1s 2s 2p 3s 1s 2s 2p 1s 2s 2p 3s 3p 1s 2s 2p 3s 3p
HL only responsible for s,p,d,f electron configurations

9. THE IONIC BOND
Ionic bonds are formed between elements whose atoms tend to ―lose‖
electrons to gain the nearest noble gas electronic configuration and those
which tend to ―gain‖ electrons. The electrons are transferred from one atom to
the other.
Sodium Chloride
+
Na ——> Na + e¯ and Cl + e¯ ——> Cl¯
2,8,1 2,8 2,8,7 2,8,8
2 2 6 1 2 2 6 2 2 6 2 5 2 2 6 2 6
or 1s 2s 2p 3s 1s 2s 2p 1s 2s 2p 3s 3p 1s 2s 2p 3s 3p
both species end up with the electronic configuration of the nearest noble gas
the resulting ions are held together in a crystal lattice by electrostatic attraction.

10. SODIUM CHLORIDE
Na Cl
SODIUM ATOM CHLORINE ATOM
2,8,1 2,8,7

11. SODIUM CHLORIDE
+
Na Cl
SODIUM ION CHLORIDE ION
2,8 2,8,8
both species now have ‘full’ outer shells; ie they
have the electronic configuration of a noble gas

12. THE IONIC BOND
FORMATION OF MAGNESIUM CHLORIDE
e¯
Cl
ELECTRON
Mg
TRANSFER
Cl
e¯
2+
Mg ——> Mg + 2e¯ and 2Cl + 2e¯ ——> 2 Cl¯

13. MAGNESIUM CHLORIDE
Cl
Mg CHLORINE ATOMS
2,8,7
MAGNESIUM ATOM Cl
2,8,2

14. MAGNESIUM CHLORIDE
Cl
2+
Mg CHLORIDE IONS
2,8,8
MAGNESIUM ION Cl
2,8

15. THE FORMATION OF POSITIVE IONS
• also known as cations; they are smaller than the original atom.
• formed when electrons are removed from atoms.
• the energy associated with the process is known as the ionisation energy
st
Recall: 1st IONISATION ENERGY (1 I.E.)
The energy required to remove one mole of electrons (to infinity) from the one
mole of gaseous atoms to form one mole of gaseous positive ions.
+ +
e.g. Na(g) ——> Na (g) + e¯ or Mg(g) ——> Mg (g) + e¯
Other points (HL topic 12)
nd rd
Successive IE‘s (2 , 3 , etc) get larger as the proton:electron ratio increases.
Large jumps in value occur when electrons are removed from shells nearer the
nucleus because there is less shielding and more energy is required to
overcome the attraction.
If the I.E. values are very high, covalent bonding will be favoured (e.g.
beryllium).

16. THE FORMATION OF NEGATIVE IONS
• known as anions
• are slightly larger than the neutral atom - electron repulsion in outer shell
• formed when electrons are added to atoms
• energy is released as the nucleus pulls in an electron
• this energy is the electron affinity.
ELECTRON AFFINITY
The energy change when one mole of gaseous atoms acquires one mole of
electrons (from infinity) to form one mole of gaseous negative ion
e.g. Cl(g) + e¯ ——> Cl¯(g) and O(g) + e¯ ——> O¯(g)
The greater the effective nuclear charge (E.N.C.)of a species, the easier an
electron is attracted.

17. Ions form from a tendency toward a lower energy,
stable, noble gas electron configuration
Transition metals have more complex electron arrangements
(d – subshell HL material) thus can form more than one ion.

18. IONIC COMPOUNDS - CRYSTAL LATTICE STRUCTURE
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
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.

19. 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
+
Each Na is surrounded by 6 Cl¯
+
and each Cl¯ is surrounded by 6 Na

20. 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 similar
ions being adjacent. The repulsion splits the crystal.
Electrical don‘t conduct when solid - ions 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 is a polar solvent and stabilises the separated ions.

21. IONIC COMPOUNDS - ELECTRICAL
PROPERTIES
- -
SOLID IONIC Cl Cl
+ +
Na Na IONS ARE HELD STRONGLY TOGETHER
COMPOUNDS DO - -
Cl Cl
+
+
Na + IONS CAN‘T MOVE
NOT CONDUCT Na
ELECTRICITY - - - IONS CAN‘T MOVE
Cl Cl
+ +
Na Na
MOLTEN IONIC - IONS HAVE MORE FREEDOM IN A
COMPOUNDS DO Na
+ Cl LIQUID SO CAN MOVE TO THE
CONDUCT ELECTRODES
ELECTRICITY - Na
+
Cl
+
- Na
SOLUTIONS OF IONIC Cl DISSOLVING AN IONIC COMPOUND
COMPOUNDS IN Na
+
IN WATER BREAKS UP THE
WATER DO CONDUCT - STRUCTURE SO IONS ARE FREE TO
Cl MOVE TO THE ELECTRODES
ELECTRICITY

22. Many ionic compounds are soluble in water - dissolving