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Groups in the periodic table - AQA SynergyGroup 7 - displacement reactions

Elements in the same group of the periodic table show trends in physical properties, such as boiling point. They have the same number of electrons in their outer shell, so they are similar in their chemical properties.

Part of Combined ScienceBuilding blocks for understanding

Group 7 - displacement reactions

A more can a less reactive halogen from of its . For example, chlorine is more reactive than iodine. A solution of chlorine can displace iodine from potassium iodide solution:

chlorine + potassium iodide 鈫 potassium chloride + iodine

Cl2(aq) + 2KI(aq) 鈫 2KCl(aq) + I2(aq)

The reaction mixture turns darker as iodine solution forms.

The slideshow shows what happens when solutions of chlorine, bromine and iodine are added to various potassium salts.

Image gallerySkip image gallerySlide 1 of 6, Chlorine water is added to three test tubes containing potassium chloride, potassium bromide and potassium iodide., Adding chlorine, bromine and iodine to halogen salts Chlorine water is added to three solutions

Question

Write the word equation for the displacement reaction of chlorine solution with sodium bromide solution.

Question

Write a balanced equation for the displacement reaction of bromine solution with sodium iodide solution.

Question

Can iodine displace chlorine from sodium chloride solution? Explain your answer.

Explaining the trend in reactivity

When a group 7 element takes part in a reaction, its each gain one . These atoms form negatively charged . The ions have a stable arrangement of electrons, with a complete outer shell.

Going down group 7:

  • the atoms become larger
  • the outer shell becomes further from the
  • the force of attraction between the nucleus and the outer shell decreases
  • an outer electron is gained less easily
  • the halogen becomes less reactive

The periodic table, containing all the known elements, arranged in groups and periods