Who this is for: Cambridge IGCSE Coordinated Science (0654) students who want ions and ionic bonds — how they form and what properties they give — to become a reliable source of marks instead of a dot-and-cross guessing exercise.
What query it owns: how to understand and revise ions and ionic bonds in Cambridge IGCSE Coordinated Science.
Why this is safe: this page owns the ions-and-ionic-bonds revision-guide angle, while Tutopiya’s Ions And Ionic Bonds subtopic page owns the learning resource and the free Ions And Ionic Bonds quiz owns the practice.

Ionic bonding holds together compounds such as sodium chloride and magnesium oxide. Cambridge IGCSE Coordinated Science (0654) expects you to explain how ions form by electron transfer, draw dot-and-cross diagrams, and link the giant ionic lattice to properties like high melting points and electrical conductivity when molten or dissolved. This guide links each idea to what examiners reward.

Key takeaways

• An ion is a charged atom or group of atoms — cations (+) form when metals lose electrons; anions (−) form when non-metals gain electrons.
• Ionic bonds are strong electrostatic attractions between oppositely charged ions.
• Ionic compounds form giant ionic lattices — regular 3D arrangements of ions.
• Ionic compounds have high melting/boiling points, conduct electricity when molten or in aqueous solution, and are usually soluble in water.
• Dot-and-cross diagrams show electron transfer from metal to non-metal.

What are ions and ionic bonds in Cambridge IGCSE Coordinated Science?

When a metal atom loses one or more electrons it becomes a positive ion (cation). When a non-metal atom gains electrons it becomes a negative ion (anion). The oppositely charged ions attract strongly, forming an ionic bond. The result is a giant lattice of ions held together by electrostatic forces — not separate molecules.

You can read the full explanation, dot-and-cross diagrams and notes on Tutopiya’s Ions And Ionic Bonds subtopic page before you attempt questions.

How common ions form

Atom	Change	Ion formed	Charge
Sodium (Na)	Loses 1 electron	Na⁺	+1
Magnesium (Mg)	Loses 2 electrons	Mg²⁺	+2
Chlorine (Cl)	Gains 1 electron	Cl⁻	−1
Oxygen (O)	Gains 2 electrons	O²⁻	−2

Properties of ionic compounds

Property	Explanation
High melting/boiling point	Strong electrostatic forces between ions in lattice; much energy needed to break
Conducts when molten/dissolved	Ions are free to move and carry charge
Does not conduct when solid	Ions are fixed in the lattice
Brittle	Layers shift on impact; like charges repel and crystal shatters
Soluble in water	Many ionic compounds dissolve; water molecules surround ions

Ions and ionic bonds in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical ionic bonding stem
Explain how	Describe ion formation	”Explain how a sodium ion forms from a sodium atom.”
Draw	Dot-and-cross diagram	”Draw a dot-and-cross diagram for NaCl.”
State properties	Link to structure	”State two properties of ionic compounds.”
Explain why	Connect structure to property	”Explain why solid NaCl does not conduct electricity.”

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

1. “Explain how a sodium ion, Na⁺, forms from a sodium atom.” Sodium atom has 1 outer electron; it loses this electron to form Na⁺ with a +1 charge and stable electron configuration. Mark-scheme reward: loses electron and +1 charge.
2. “Explain why molten sodium chloride conducts electricity but solid sodium chloride does not.” In the solid, ions are fixed in the lattice and cannot move. When molten, ions are free to move and carry electric charge. Reward: fixed vs mobile ions.
3. “State the formula of the ion formed when a magnesium atom loses its outer electrons.” Mg²⁺. Reward: correct ion formula with charge.

Test yourself with the Ions And Ionic Bonds quiz once you can draw dot-and-cross diagrams and explain ionic properties.

How ions and ionic bonds connect to the rest of Coordinated Science

Ionic bonding builds on Atomic Structure And The Periodic Table and contrasts with Molecules And Covalent Bonds. It underpins electrolysis and salt preparation. The Cambridge IGCSE Coordinated Science resource hub links every Atoms, Elements And Compounds subtopic.

Common mistakes students make

• Drawing covalent dot-and-cross diagrams for ionic compounds (show transfer, not sharing).
• Saying ionic compounds conduct in the solid state (only when molten or dissolved).
• Confusing cations (+) with anions (−).
• Forgetting to show charges on ions in diagrams.
• Stating metals gain electrons (metals lose electrons to form cations).

When you need more support

If ionic bonding questions keep costing marks, work through the Ions And Ionic Bonds quiz, then get focused help from a Cambridge IGCSE Coordinated Science tutor.

Frequently asked questions

Is ionic bonding hard in Coordinated Science? The electron transfer model is straightforward — marks are lost on dot-and-cross diagrams and conductivity explanations.

What is the difference between a cation and an anion? A cation is a positive ion (metal loses electrons); an anion is a negative ion (non-metal gains electrons).

Why do ionic compounds have high melting points? Strong electrostatic forces between oppositely charged ions in the giant lattice require a lot of energy to overcome.

How do I revise ions and ionic bonds effectively? Practise dot-and-cross diagrams for NaCl and MgO, link properties to lattice structure, then take the Ions And Ionic Bonds quiz.

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