Ions and ionic bonding Cambridge IGCSE Co-ordinated Sciences (9–1) revision
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In plain words
Metals want to lose their outer electrons; non-metals want to gain some. When they meet, the metal hands electrons over. Now one is a positive ion and the other a negative ion, and opposite charges attract strongly. Millions of them stack up in a giant lattice. That attraction is the ionic bond.
Three things to know
- Metal atoms lose their outer electrons and become positive ions. Non-metal atoms gain electrons and become negative ions. Both end up with full outer shells.
- An ionic bond is the strong electrostatic attraction between oppositely charged ions. The ions are arranged in a giant lattice.
- Ionic compounds have high melting points, and conduct electricity when molten or dissolved (the ions can move) but not when solid.
Worked example
Work out the formula of aluminium chloride. (Ions: Al³⁺ and Cl⁻.)
- The charges must add up to zero.
- One Al³⁺ has a charge of 3+, so it needs three Cl⁻ ions (3−).
- AlCl₃.
Tips and tricks
- To write a formula, swap the sizes of the charges: Al³⁺ and O²⁻ give Al₂O₃. Then cancel down if you can.
- Conducts when molten or dissolved "because the ions are free to move". Never say electrons for an ionic compound.
It lands in your notebook with its questions as flashcards.
Ions and ionic bonding: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What is the charge on the ion formed by a Group 2 metal?
It loses its two outer electrons.
What holds the ions together in an ionic compound?
Positive and negative ions attract each other strongly.
Which substance is ionic?
It is made from a metal and a non-metal.
What is the formula of calcium oxide? (Ions: Ca²⁺ and O²⁻.)
One 2+ ion balances one 2− ion.
When do ionic compounds conduct electricity?
The ions must be free to move.
What is the formula of aluminium oxide? (Ions: Al³⁺ and O²⁻.)
Two 3+ ions (6+) balance three 2− ions (6−).
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
4 questions, 9 marks. Write your answers on paper, then check them.
Ions and ionic bonding
Cambridge IGCSE Co-ordinated Sciences (9–1) 0973 · 9 marks · papermunch.org
Name ______________________________ Date ______________
Describe how the ions in sodium chloride are formed from sodium and chlorine atoms.[3]
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A sodium atom loses its one outer electron to form Na⁺. A chlorine atom gains that electron to form Cl⁻. Both now have full outer shells.
Explain why sodium chloride has a high melting point.[2]
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There are strong electrostatic attractions between the oppositely charged ions throughout the giant lattice, and a lot of energy is needed to overcome them.
Explain why sodium chloride conducts electricity when molten but not when solid.[2]
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In the solid the ions are held in fixed positions. When molten the ions are free to move and carry the charge.
Work out the formula of magnesium chloride. (Ions: Mg²⁺ and Cl⁻.)[2]
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MgCl₂. Two Cl⁻ ions are needed to balance the charge of one Mg²⁺.
Answers: Ions and ionic bonding
- 1. A sodium atom loses its one outer electron to form Na⁺. A chlorine atom gains that electron to form Cl⁻. Both now have full outer shells.
- 2. There are strong electrostatic attractions between the oppositely charged ions throughout the giant lattice, and a lot of energy is needed to overcome them.
- 3. In the solid the ions are held in fixed positions. When molten the ions are free to move and carry the charge.
- 4. MgCl₂. Two Cl⁻ ions are needed to balance the charge of one Mg²⁺.