Starter quiz
- Match the keyword to the correct statement.
- displacement⇔when an element replaces a less reactive element in a compound ✓
- halide⇔name of the salts formed from halogens ✓
- halogen⇔non-metallic elements in Group 7 that react with metals to form salt ✓
- salts⇔ionic compounds made of positive and negative ions ✓
- What happens when Group 2 elements react with a halogen?
- Each Group 2 atom transfers an outer electron to a Group 7 atom.
- Each Group 2 atom transfers two outer electrons to a Group 7 atom.
- Each Group 2 atom transfers two outer electrons to two separate Group 7 atoms. ✓
- Group 2 atoms form positively charged ions. ✓
- Group 2 atoms form negatively charged ions.
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- Which is the correct symbol equation for a reaction between magnesium and chlorine?
- magnesium + chlorine → magnesium chloride
- Mg(s) + Cl (g) → MgCl (s)
- Mg(s) + 2Cl(g) →MgCl₂(s)
- Mg(s) + Cl₂ (g) → MgCl₂ (s) ✓
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- Which is the correct formula for barium bromide?
- BaBr
- BBr₂
- Ba₂Br₂
- BaBr₂ ✓
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- Which of the following experiments will result in a displacement reaction?
- iodine + potassium bromide
- iodine + potassium chloride
- bromine + potassium chloride
- chlorine + potassium iodide ✓
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- ______ + F₂ → 2CsF
- '2Cs' ✓
Exit quiz
- What does a negative charge on an ion mean?
- An atom has lost an electron from its outer shell.
- An atom has gained an electron. ✓
- There are more electrons than protons present in the ion ✓
- There are more protons than electrons present in the ion.
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- What type of reaction occurs when a metal atom loses an outer electron to become a positive stable ion?
- reduction
- neutralisation
- decomposition
- oxidation ✓
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- Choose the correct half equation.
- Na → Na⁺ + e⁻ ✓
- Na → Na²⁺ + 2e⁺
- Na → Na⁻ + e⁺
- 2Na → 2Na⁻ + e⁺
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- Which one of the following half equations is correct?
- Cl₂ + 2e⁻ → 2Cl⁻ ✓
- Cl₂ + 2e⁻ → Cl₂⁻
- Cl₂ + 2e⁻ → Cl₂²⁻
- Cl₂ + 2e⁻ → Cl⁻
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- Which half equations show a reduction reaction?
- Mg → Mg²⁺ + 2e⁻
- Br₂ + 2e⁻ → 2Br⁻ ✓
- Na → Na⁺ + e⁻
- O₂ + 4e⁻ → 2O²⁻ ✓
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- Look at this displacement reaction: F₂ (aq) + 2 KI (aq) → I₂ (aq) + 2KF (aq). Identify a spectator ion.
- K⁺ ✓
- F₂
- K⁺ I⁻
- I⁻
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Worksheet
Presentation
Video
Lesson Details
Key learning points
- Reduction is the gain of electrons, and oxidation is the loss of electrons.
- Displacement reactions are often examples of redox reactions.
- Half equations show which elements are oxidised, and which are reduced.
Common misconception
Pupils can confuse oxidation and reduction when involving electrons. They often mistake a positive charge on an ion as meaning electrons have been added and vice versa for negative ions.
It is very important to teach from first principles what causes the charges and then work up to half equations where the pupils can see the electrons in the equations, finally combining these to form ionic equations.
Keywords
Oxidation - A type of reaction in which a substance gains oxygen or loses electrons.
Half equation - A chemical equation used to show the electrons lost in oxidation or the electrons gained in reduction.
Reduction - A type of reaction in which a substance loses oxygen or gains electrons.
Redox - A redox reaction is one in which a substance is oxidised and another is reduced.
Ionic equation - A chemical equation in which reacting ions are shown; unreacting ions (spectator ions) are not included.