REVISION NOTES
IGCSE Edexcel Chemistry
1.6 Ionic Bonding
1.6.1 Understand how ions are formed by electron loss or gain
IONS
- Ions are formed when atoms gain or lose electron(s)
- In order to form full electron shells (octet rule)
- So that it can be more stable
- Metals tend to lose electrons → forming positive ions (cations)
- Nonmetals tend to gain electrons → forming negative ions (anions)
Formation of Cations (Metal Losing Electrons)
![](https://resource.studiaacademy.com/wp-content/uploads/2022/04/POC-Illustration-24-1.png)
Formation of Anions(Nonmetal Gaining Electrons)
![](https://resource.studiaacademy.com/wp-content/uploads/2022/04/POC-Illustration-25-1.png)
1.6.2 Know the charges of these ions:
- Metals in Groups 1, 2 and 3
- Non-metals in Groups 5, 6 and 7
- Ag+, Cu2+, Fe2+, Fe3+, Pb2+, Zn2+
- Hydrogen (H+), Hydroxide (OH–), Ammonium (NH4+), Carbonate (CO32–), Nitrate (NO3–), Sulphate (SO42–).
Metals and Nonmetals in Group 1, 2, 3, 5, 6 and 7:
![edexcel_igcse_chemistry_topic 06 tables_ionic bonding_001_relationship between group number and metal charge](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-06-tables_ionic-bonding_001_relationship-between-group-number-and-metal-charge.png)
Common Groups (Polyatomic Ions):
![edexcel_igcse_chemistry_topic 06 tables_ionic bonding_002_polyatomic ions](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-06-tables_ionic-bonding_002_polyatomic-ions.png)
1.6.3 Write formulae for compounds formed between the ions listed above
IONIC COMPOUNDS
- Ionic compounds are formed when a positive ion combines with a negative ion
- The net charge of an ionic compound is 0
- Number of ions should be multiplied to make sure the sum of charge = 0
- Cross-multiply each ion with the charge of the other ion
- It can be applied to common groups (polyatomic ions) as well
EXAMPLE
What is the formula of aluminium sulphate?
Al is in group III
→ charge = 3+
→ Al3+
Sulphate is a common ion
→ SO42-
![edexcel_igcse_chemistry_topic 06_ionic bonding_003_molecular formula trick with ion charges](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-06_ionic-bonding_003_molecular-formula-trick-with-ion-charges.png)
1.6.4 Draw dot-and-cross diagrams to show the formation of ionic compounds by electron transfer, limited to combinations of elements from Groups 1, 2, 3 and 5, 6, 7 only outer electrons need be shown
Ionic compounds are formed when there is electron transfer between metals and nonmetals
- Metals lose electrons
- Nonmetals gain electrons
- Electron(s) gained by the nonmetal should be annotated by a different symbol than the symbols of electrons in the nonmetal
- After ions are formed, there should be square bracket and charge on the top right corner
![edexcel_igcse_chemistry_topic 06_ionic bonding_004_ionic bonding labelled diagram](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-06_ionic-bonding_004_ionic-bonding-labelled-diagram.png)
EXAMPLE
Draw the dot-and-cross diagram to show the formation of the compound CaO
![edexcel_igcse_chemistry_topic 06_ionic bonding_005_ionic dot and cross diagram charges](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-06_ionic-bonding_005_ionic-dot-and-cross-diagram-charges.png)
1.6.5 Understand ionic bonding in terms of electrostatic attractions
IONIC BONDING
- Electrostatic attraction force between two oppositely charged ions
- Exact terminologies should be memorised
1.6.6 Understand why compounds with giant ionic lattices have high melting and boiling points
STRUCTURE OF IONIC COMPOUNDS
- Ionic compounds are giant lattice structure of ions
- Due to the strong electrostatic attraction forces, ionic compounds have high melting and boiling points
- Ionic compounds are usually solid at room temperature and are non-volatile
- They are usually water soluble as both ionic compounds and water are polar substances
![edexcel_igcse_chemistry_topic 06 tables_ionic bonding_003_giant ionic lattice compounds physical properties](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-06-tables_ionic-bonding_003_giant-ionic-lattice-compounds-physical-properties.png)
![edexcel_igcse_chemistry_topic 06_ionic bonding_006_giant ionic lattice diagram NaCl sodium chloride](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-06_ionic-bonding_006_giant-ionic-lattice-diagram-NaCl-sodium-chloride.png)
1.6.7 Know that ionic compounds do not conduct electricity when solid, but do conduct electricity when molten and in aqueous solution
ELECTRICAL CONDUCTIVITY OF IONIC COMPOUNDS
For a substance to conduct electricity, there should be free-moving, charged particles, for example:
- Ions in solution
- Free electrons in metal
![edexcel_igcse_chemistry_topic 06 tables_ionic bonding_004_conductivity of ionic compounds in solid vs molten or aqueous state](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-06-tables_ionic-bonding_004_conductivity-of-ionic-compounds-in-solid-vs-molten-or-aqueous-state.png)
![edexcel_igcse_chemistry_topic 06_ionic bonding_008_electrical conductivity of ionic compounds molten and solid diagram](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-06_ionic-bonding_008_electrical-conductivity-of-ionic-compounds-molten-and-solid-diagram.png)
![edexcel_igcse_chemistry_topic 06_ionic bonding_007_ions dissolving in water](https://resource.studiaacademy.com/wp-content/uploads/2023/08/edexcel_igcse_chemistry_topic-06_ionic-bonding_007_ions-dissolving-in-water.png)