Who this is for: Cambridge IGCSE Chemistry (0620) students who can draw dot-and-cross diagrams but lose explain marks on why ions form, ionic lattice structure, or properties of ionic compounds.
What query it owns: how to understand and revise ions and ionic bonds in Cambridge IGCSE Chemistry.
Why this is safe: this page owns the ionic-bonding revision-guide angle in the cambridge-igcse-chemistry folder, while Tutopiya’s Ions and Ionic Bonds subtopic page owns the learning resource and the free Ions and Ionic Bonds quiz owns the practice.

An ion is a charged particle formed when an atom gains or loses electrons. Ionic bonding is the electrostatic attraction between oppositely charged ions in a giant ionic lattice. Metals in Groups I and II and non-metals in Groups VI and VII commonly form ionic compounds such as sodium chloride. Cambridge IGCSE Chemistry (0620) tests diagrams, electron transfer explanations, and properties linked to structure.

Key takeaways

• Metal atoms lose electrons → positive ions (cations); non-metal atoms gain electrons → negative ions (anions).
• Ionic compounds form giant ionic lattices of alternating positive and negative ions.
• Properties: high melting/boiling points, conduct electricity when molten or in solution, brittle, soluble in water (many).
• Dot-and-cross diagrams show electron transfer — only outer-shell electrons are shown.
• Confirm with the Ions and Ionic Bonds quiz.

What are ions and ionic bonds?

Ions form when atoms gain or lose electrons to achieve a stable electron arrangement (often a full outer shell). Ionic bonding is the strong electrostatic attraction between oppositely charged ions arranged in a regular giant lattice. In Cambridge IGCSE Chemistry (0620) you draw formation diagrams, name ions, and explain properties from structure.

Read the full notes on Tutopiya’s Ions and Ionic Bonds subtopic page.

Ion formation — summary table

Atom type	What happens	Ion formed	Example
Group I metal	Loses 1 electron	+1 cation	Na⁺
Group II metal	Loses 2 electrons	+2 cation	Mg²⁺
Group VI non-metal	Gains 2 electrons	−2 anion	O²⁻
Group VII non-metal	Gains 1 electron	−1 anion	Cl⁻

Properties of ionic compounds — comparison with covalent

Property	Ionic compound	Simple covalent molecule
Melting/boiling point	High	Low
Electrical conductivity (solid)	Poor	Poor
Electrical conductivity (molten/aqueous)	Good	Poor
Solubility in water	Often soluble	Often insoluble

How to answer ionic bonding questions — step by step

1. Identify metal and non-metal — ionic bonding is typically between them.
2. Count outer electrons — how many are lost/gained to reach stable arrangement.
3. Draw dot-and-cross showing transfer of outer electrons only.
4. Write ion formulae with charges — total positive charge = total negative charge.
5. For explain questions, link properties to strong electrostatic forces in the lattice.
6. Test with the free Ions and Ionic Bonds quiz.

Past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical stem
Draw	Dot-and-cross diagram	”Draw a dot-and-cross diagram for magnesium chloride.”
Explain	Why ions form / property link	”Explain why sodium chloride has a high melting point.”
State	Short fact	”State the charge on a chloride ion.”
Describe	Structure	”Describe the structure of an ionic compound.”

Worked exam-style stems (how to answer the wording)

1. “Draw a dot-and-cross diagram to show the formation of sodium chloride.” Show Na losing 1 electron to Cl; Na⁺ and Cl⁻ with correct outer shells. Draw = accurate electron transfer, not shared pairs.
2. “Explain why solid sodium chloride does not conduct electricity but molten sodium chloride does.” Solid: ions fixed in lattice, cannot move. Molten: ions free to move and carry charge. Explain = link conductivity to ion mobility.
3. “State the formula of the ion formed when a magnesium atom loses its outer electrons.” Mg²⁺. State = concise answer with charge.

Practise more on the Atoms topical past paper questions.

How ionic bonding connects to covalent bonding

Ionic bonding (electron transfer) contrasts with Simple Molecules and Covalent Bonds (electron sharing). Know when to choose ionic vs covalent: metal + non-metal usually ionic; non-metal + non-metal usually covalent. The Cambridge IGCSE Chemistry hub links all bonding subtopics.

Common mistakes students make

• Drawing shared pairs in ionic diagrams — ionic bonding is transfer, not sharing.
• Forgetting ion charges in formulae (e.g. writing NaCl₂).
• Explaining high melting point as “strong covalent bonds” — ionic lattices have strong electrostatic forces.
• Saying ionic solids conduct — only molten or aqueous ionic compounds conduct.
• Skipping the Ions and Ionic Bonds quiz.

When you need more support

If dot-and-cross and explain questions keep scoring partial marks, drill the topical past paper questions and book a Cambridge IGCSE Chemistry tutor.

Frequently asked questions

What is the difference between an atom and an ion? An ion is a charged particle formed when an atom gains or loses electrons; an atom is neutral.

Why do ionic compounds have high melting points? Strong electrostatic attraction between oppositely charged ions in the lattice requires much energy to overcome.

Do all metals form ionic bonds? At IGCSE, focus on Groups I and II metals with Group VI/VII non-metals; transition metals are more complex.

How do I revise ionic bonding effectively? Read subtopic notes, practise draw/explain stems, take the Ions and Ionic Bonds quiz, then compare with covalent bonding.

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