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    Ionic equations: reactions of Group 1 and Group 7

    I can write balanced ionic equations and half equations for the reactions of Group 1 and 7 elements.

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      Ionic equations: reactions of Group 1 and Group 7

      I can write balanced ionic equations and half equations for the reactions of Group 1 and 7 elements.

      Lesson details

      Key learning points

      1. Reduction is the gain of electrons, and oxidation is the loss of electrons.
      2. Displacement reactions are often examples of redox reactions.
      3. Half equations show which elements are oxidised, and which are reduced.

      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.

      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.

      Pupils need much practise so many half equation examples of species being both oxidised and reduced helps.
      Teacher tip

      Equipment

      None required.

      Licence

      This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

      Lesson video

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      Prior knowledge starter quiz

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      6 Questions

      Q1.
      Match the keyword to the correct statement.

      Correct Answer:displacement ,when an element replaces a less reactive element in a compound

      when an element replaces a less reactive element in a compound

      Correct Answer:halide,name of the salts formed from halogens

      name of the salts formed from halogens

      Correct Answer:halogen,non-metallic elements in Group 7 that react with metals to form salt

      non-metallic elements in Group 7 that react with metals to form salt

      Correct Answer:salts,ionic compounds made of positive and negative ions

      ionic compounds made of positive and negative ions

      Q2.
      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.
      Correct answer: Each Group 2 atom transfers two outer electrons to two separate Group 7 atoms.
      Correct answer: Group 2 atoms form positively charged ions.
      Group 2 atoms form negatively charged ions.

      Q3.
      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)
      Correct answer: Mg(s) + Cl₂ (g) → MgCl₂ (s)

      Q4.
      Which is the correct formula for barium bromide?

      BaBr
      BBr₂
      Ba₂Br₂
      Correct answer: BaBr₂

      Q5.
      Which of the following experiments will result in a displacement reaction?

      iodine + potassium bromide
      iodine + potassium chloride
      bromine + potassium chloride
      Correct answer: chlorine + potassium iodide

      Q6.
      + F₂ → 2CsF

      Correct Answer: 2Cs

      Assessment exit quiz

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      6 Questions

      Q1.
      What does a negative charge on an ion mean?

      An atom has lost an electron from its outer shell.
      Correct answer: An atom has gained an electron.
      Correct answer: There are more electrons than protons present in the ion
      There are more protons than electrons present in the ion.

      Q2.
      What type of reaction occurs when a metal atom loses an outer electron to become a positive stable ion?

      reduction
      neutralisation
      decomposition
      Correct answer: oxidation

      Q3.
      Choose the correct half equation.

      Correct answer: Na → Na⁺ + e⁻
      Na → Na²⁺ + 2e⁺
      Na → Na⁻ + e⁺
      2Na → 2Na⁻ + e⁺

      Q4.
      Which one of the following half equations is correct?

      Correct answer: Cl₂ + 2e⁻ → 2Cl⁻
      Cl₂ + 2e⁻ → Cl₂⁻
      Cl₂ + 2e⁻ → Cl₂²⁻
      Cl₂ + 2e⁻ → Cl⁻

      Q5.
      Which half equations show a reduction reaction?

      Mg → Mg²⁺ + 2e⁻
      Correct answer: Br₂ + 2e⁻ → 2Br⁻
      Na → Na⁺ + e⁻
      Correct answer: O₂ + 4e⁻ → 2O²⁻

      Q6.
      Look at this displacement reaction: F₂ (aq) + 2 KI (aq) → I₂ (aq) + 2KF (aq). Identify a spectator ion.

      Correct answer: K⁺
      F₂
      K⁺ I⁻
      I⁻

      Lesson appears in

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