Ionic Bonding
Chemistry: AQA A Level, topic 1.3.1
Ionic Bonds
Ionic bonding is a type of bonding between oppositely charged ions.
-min,w_800.jpg)
Ionic bonds
- Ionic bonding is the electrostatic attraction between ions of opposite charges.
- Ionic bonds are very strong. Ionic bonds are much stronger than any type of intermolecular force, but are generally weaker than covalent bonds.
Noble gas configurations
- Ions form to make noble gas configurations.
- An atom will lose or gain electrons until it has the same electron configuration as a noble gas (i.e. a full outer shell).
Forming positive ions (e.g. Na+)
- Group 1 atoms will lose one electron to form a full outer shell.
- Group 2 atoms will lose two electrons to form a full outer shell.
- Group 3 atoms will lose three electrons to form a full outer shell.
Forming negative ions (e.g. F−)
- Group 6 atoms will gain two electrons to form a full outer shell.
- Group 7 atoms will gain one electron to form a full outer shell.
Compound Ions
A compound ion is an ion which is made of multiple atoms.
Compound ions
- There are a few examples you need to know:
- Carbonate ions: CO32-
- Nitrate ions: NO3-
- Hydroxide ions: OH-
- Sulfate ions: SO42-
- Ammonium ions: NH4+
%202.1.2.2%20-%20Ca%20and%20O%20atoms%20%E2%86%92%20Ca2+%20and%20O2-%20ions%20(1)-min,w_800.jpg)
Formulae
- Ionic formulae can be calculated by balancing charge.
- The principle of electroneutrality states that the overall charge must be zero.
- Add or subtract cations (positive ions) or anions (negative ions) to find a neutral formula.
Ionic Lattices
Ionic compounds have a lattice structure.
%202.1.3.1%20-%20Ionic%20lattice%20represented%20using%20both%20the%20space-filling%20model%20and%20ball%20and%20stick%20model,w_800.png)
Giant ionic lattices
- Ionic compounds have what is called a giant ionic lattice structure.
- This means that the structure is made of repeating units of identical structure.
- Different compounds can have very different lattices.
- E.g. Sodium chloride (NaCl) has a cube-shaped lattice.
%202.2.3.1%20-%20NaCl%20ionic%20lattice-min,w_800.png)
Properties
- Ionic compounds have certain specific properties:
- They dissolve in water - this is because water is polar.
- They conduct electricity when molten or dissolved.
- This is because the ions can move and carry charge when molten or solvated.
- They have high melting points.
- This is because the ionic bonds are very strong.
Test yourself on Ionic Bonding
What kind of attraction exists in ionic bonding?
Which of the following is true of ions?
What is the formula of the nitrate ion?
What is the formula of the sulfate ion?
What is the formula of the hydroxide ion?