1. Chapter 6
Ionic Bonds

2. Types of Bonding
Atoms are rarely found individually in nature because atoms try to achieve a more stable structure.
Atoms can become stable in one of three ways:
By giving electrons to another atom
By taking electrons from another atom
By sharing electrons with another atom
Metallic bonds = metallic atoms combine to form a metallic lattice
Ionic bonds = metallic atoms combine with non-metallic atoms
Covalent bonds = non-metallic bonds combine

3. Ions - review Atoms which gain or lose electrons are called ions
Positive ions = cations
Negative ions = anions

4. IONIC BONDING
Metals and non-metals react because electrons lost by metals are taken up by electronegative non-metals. This transfer of electrons is an ionic bond. Cations and Anions are oppositely charged and attract each other by electrostatic attraction.

5. IONIC BONDING
Note: the bonded ionic compound is more stable than the unbonded form and has different properties from those of the original elements. The general name for an ionic compound (a substance formed from a reaction between a metal and non-metal, is a salt)

6. Electron Shell Diagrams
Using electron shell diagrams and simple equations to show the ionic bonding between a metal and a non-metal:
Be and Cl
Li and F
Al and S
Na and N
Mg and S
Mg and F
Mg2+ + 2Cl MgCl2

7. Ionic Lattices Major features:
Ionic compounds form crystals that are composed of three dimensional arrays of positive metal ions and negative non-metal ions
These are called ionic network lattices and are held together by strong electrostatic forces between the oppositely charged particles
The ions are arranged in a regular repeating pattern and pack together so that a positive ion is only surrounded by negatives and a negative ion is only surrounded by positive ions
The numbers of positive ions and negative ions depend on making the compound neutral

8. Ionic Lattices
Ionic compounds are made up of two ions that have opposing charges. The electrostatic forces of attraction holding them together are strong. As a result, they are:
Usually crystalline solids
Have high melting and boiling points, as a large amount of energy is needed to separate the ions
Will not conduct electricity in the solid state as the ions are not free to move

9. Ionic Lattices
Are hard, since the surface of the crystal is not easily scratched due to the strong ionic bonds
Will often dissolve in water to form free mobile ions as water disrupts the rigid crystal structure
Will conduct electricity when in solution as ions are free to move. Solution is called an electrolyte.
Are brittle, as moving the crystal structure causes ions of like charge to come into contact and the repulsion shatters the structure

10. Ionic Bonding Polyatomic ions – Some ions contain more than one atom.
Eg. Carbonate CO3, Ammonium NH4, Hydroxide OH
If more than one of these ions is required then you need to use brackets eg. Mg(OH)2
Ions of elements with different valencies –
Some elements form ions with different charges. In this situation, you need to specify the electrovalency by placing the roman numeral of the charge after the metal in the name of the compound.
Eg. Iron (II) Chloride contains the Fe2+ ion, formula is FeCl2
Iron (III) Chloride contains the Fe3+ ion, formula is FeCl3