This topic accounts for approximately 9% of your exam marks.
stable
Medium
Stable9%
Ion formation, lattice structures and properties of ionic compounds tested consistently.
The charges of a fixed set of common ions must be learnt by heart.
Positive ions (cations)
Ion
Charge
Example
Group 1 metal
1+
Li⁺, Na⁺, K⁺
Group 2 metal
2+
Mg²⁺, Ca²⁺
Group 3 metal
3+
Al³⁺
Silver
1+
Ag⁺
Copper(II)
Negative ions (anions)
Ion
Charge
Example
Group 5 non-metal
3−
N³⁻
Group 6 non-metal
2−
O²⁻, S²⁻
Group 7 non-metal
1−
F⁻, Cl⁻, Br⁻, I⁻
Hydroxide
1−
OH⁻
Polyatomic (NH₄⁺, OH⁻, NO₃⁻, CO₃²⁻, SO₄²⁻) are clusters of atoms that carry their charge as a single unit. Treat them as one piece in any formula you build
Exam tip
Defining ionic bonding
What comes up: "State what is meant by the term ionic bonding." (2 marks)
Watch out: The mark scheme rejects any response that implies covalent bonding for M2. You do not need to mention electron transfer here — the definition is purely about the nature of the force that holds the ions together, not how the ions were created.