1. Ionic Bonding What are the charges on the following ions? Na Ca Cl Al
L.O. To be able to describe ionic bonding.
To be able to explain the properties of ionic compounds.
What are the charges on the following ions?
Na Ca
Cl Al
Sr F
As O
Rb Kr

2. Very strong electrostatic attraction
Ionic Bonding
This is 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
Na+ - 1s22s22p63s0
F- - 1s22s22p6
Ions are isoelectronic with nearest noble gas

4. Ionic Bonding Group 1-3 METALS :  1+ , 2+ and 3+ ions respectively
 loss of ALL outer e- to non-metal, leaving noble gas structure ( - s2 p6 )
Group NON-METALS :
 3- , 2- and 1- ions respectively
 by gain of e- from metal to form noble gas structure ( - s2 p6 )
Group 4 :
No 4+ ions
 too much energy to remove 4 e-
No 4- ions
 too much repulsion between 4 added e-
Some 2+ ions
 lower in group eg Sn2+ and Pb2+

5. Sodium chloride Na+Cl-(s) 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)

6. Magnesium oxide Mg2+O2-(s) X
2 , 8 , 2 O X
2 , 6
O2- X
2 , 8
3D giant lattice with 1:1 ratio of ions to give electrical neutrality
Mg2+
2 , 8
Mg2+O2-(s)

7. Calcium fluoride  Ca2+ F-2(s) X F X 2 , 7 Ca 2 , 8, 8 , 2 F X 2 , 7
2 , 8 , 8
 Ca2+ F-2(s)

8. Aluminium oxide (Al3+)2(O2-)3
2 , 8 , 3 O X
2 , 6
2 aluminium atoms transfer outer electrons (6 in total), 2 to each of 3 oxygen atoms
O2- X
2 , 8
3D giant lattice with 2:3 ratio of ions to give electrical neutrality
Al3+
2 , 8
(Al3+)2(O2-)3

9. 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

10. The Sodium Chloride Lattice
= Na+
= Cl-
Each sodium ion is surrounded by six chloride ions
Each chloride ion is surrounded by six sodium ions
 6:6 coordination
 Na1Cl1 formula

11. Properties of ionic compounds
How does the giant ionic lattice structure explain the characteristic properties of ionic compounds?
- very strong inter-ionic forces to break
very high melting point
solid does not conduct electricity
- ions cannot move
conduct electricity when molten or in solution
- ions free to move

12. Evidence for ions Teacher notes
This virtual experiment illustrates how copper can be purified using electrolysis. It could be used as a precursor to running the practical in the lab or as a revision exercise.

13. Atomic vs Ionic radii
The figure shows an electron density map for aluminium. The metallic radius for aluminium is 0.1nm.
[1nm. = 10-9 m]
The ionic radius for Al3+ is nm. (4.5 x m). Why is this so much smaller than the metallic radius?

14. Ionic radii
The table below shows some values for ionic radii of atoms.
Ion
Radius (nm)
Li+
0.068 F-
0.133
Na+
0.098
Cl-
0.181 K+
Br-
0.196
Rb+
0.148 I-
0.219
The ionic radius of the cation (+ve ion) is less than that of the parent atom.
Na = nm Na+ = nm
The ionic radius of an anion (-ve ion) is greater than that of the parent atom.
Br = nm Br- = nm
Ionic radii increase down a group
Ionic radii decrease across a Period
Na+ = nm Mg2+ = nm Al3+ = nm N3- = nm O2- = nm F- = nm