C4

• Why do elements in the same group have similar chemical properties?

  They have a similar electron configuration (same number of outer shell electrons).
• What group of the periodic table are the alkali metals? Why are they called alkali metals?

  Group 1. They react with water to form alkaline solutions with a very high pH.
• What are the general properties of the alkali metals?

  • Low melting point
  • Very reactive
  • Soft
  • Low density
• What gas is produced when an alkali metal reacts with water?

  Hydrogen
• What are the products of the reaction between lithium and water?

  Lithium hydroxide

  Hydrogen
• What is the chemical equation for the reaction between sodium and water?

  2Na + 2H2O -----> 2NaOH + H2
• What is formed when an alkali metal reacts with oxygen?

  Metal oxide
• What is the chemical equation for the reaction between lithium and oxygen?

  4Li + O2 -----> 2Li2O
• What is formed when alkali metals react with chlorine?

  Metal chloride (white precipitates).
• Why are alkali metals often stored in oil?

  To prevent them reacting with oxygen and water vapour in the air.
• Why are the alkali metals very reactive?

  They have one electron in their outer shell which they need to lose to obtain a stable electron configuration.
• Explain the trend of reactivity down group 1.

  Reactivity increases down the group as the atomic radius and electron shielding increase so there is weaker attraction between the nucleus and the outer shell electron. This means the outer electron is lost more easily further down the group.
• What is the name used to describe the elements in group 0 of the periodic table?

  Noble gases
• What are the properties of the noble gases?

  • Low boiling points
  • Low density
  • Inert
• What does chemically inert mean?

  Very unreactive
• Why are the noble gases chemically inert?

  They have full outer electron shells so are very unstable.
• Describe the trend in boiling points down group 0.

  Boiling point increases.
• What are the elements in group 7 of the periodic table called?

  Halogens
• What is the colour and state of chlorine at room temperature?

  Pale green gas
• What is the colour and state of bromine at room temperature?

  Red-brown liquid
• What is the colour and state of iodine at room temperature?

  Black solid
• Why are the halogens at different states at room temperature?

  Because they have different melting and boiling points. As you go down group 7, melting and boiling point increases.
• What are the properties of halogens?

  • Increasing melting and boiling points
  • Diatomic
  • Reactive
• Halogens are diatomic. What does this mean?

  They form molecules containing two atoms. E.g. Cl2, Br2.
• What charge does a halide ion carry? Why?

  -1.

  E.g. Cl-, Br-.

  They gain one electron to obtain a fuller outer shell and a stable electron configuration.
• What is the chemical equation for the reaction between bromine and sodium?

  Br2 + 2Na -----> 2NaBr
• Describe the trend in reactivity of the halogens. How does this affect the rate of reaction?

  Reactivity decreases down the group.

  Rate of reaction also decreases down the group.
• What is formed when hydrogen reacts with a halogen?


  Hydrogen halide.

  E.g. HCl, HBr...
• Chlorine reacts with hydrogen in the presence of sunlight but bromine requires a flame? Why?

  Reactivity decreases down the group so bromine requires more energy for the reaction to occur.
• When does a halogen displacement reaction occur?

  When a more reactive halogen displaces a less reactive halogen from an aqueous solution of its halide ions.
• Why will halogen A only displace halogen B if A is above B in group 7?

  Reactivity decreases down the group. The less reactive halogen is displaced by the more unreactive halogen. For displacement to occur, halogen A would have to be more reactive than B to displace it from the ionic compound so A has to be above B.
• Which halogen can chlorine displace?


  Any halogens below chlorine in group 7.

  E.g. iodine and bromine.
• Which halogens cannot be displaced by bromine?

  Chlorine and fluorine because they are above bromine in group 7 so are more reactive.
• Why can't iodine displace chlorine or bromine from an aqueous ionic solution?

  Because iodine is below bromine and chlorine in group 7 and reactively decreases down the group. Displacement will only occur if iodine is more reactive than the halogen in the ionic compound. Iodine could displace astatine.
• Write the word equation for the reaction between chlorine and potassium bromide.

  Chlorine + Potassium bromide -----> Potassium chloride + Bromine
• Write the word equation for the reaction between bromine and calcium chloride.

  No reaction occurs because bromine can't displace chlorine.
• Write the chemical equation for the reaction between bromine and potassium iodide.

  Br2 + 2KI -----> I2 + 2KBr
• Why does reactivity decrease down group 7?

  Halogens need to gain one electron to obtain a stable electron configuration. As you go down group 7 atomic radius and electron shielding increase. Attraction between the nucleus and outer shell electrons decreases so it is harder for the atom to gain an electron meaning reactivity decreases.
• What colour are solutions of chlorine, bromine, and iodine?

  Chlorine water - colourless

  Bromine water - orange

  Iodine solution - brown
• What would you observe when chlorine is added to potassium bromide?

  Cl2 + 2KBr -----> Br2 + 2KCl

  Colour change from colourless (due to Cl2) to orange (due to Br2).