Group 7 (halogens)

• Why are group 7 elements called halogens?

  They are called halogens because they form salts when they react with metals.
• How do you know if an element is in group 7?

  If the outershell has 7 electrons.
• What is the reactivity of halogens like?

  It decreases as you go down the group.
• What are the physical properties of halogens?

  -exist as diatomic molecules (e.g Cl2, Br2, I2).

  -coloured.

  -have strong odour.

  -non metals.

  -poor conductors of heat and electricity.

  -low melting and boiling points.

  -poisonous.

  -form covalent bonds.
• What happens to the colour of halogens as you go down the group?

  Darker and deeper.
• What does chlorine look like at room temperature?

  It looks like a poisonous green gas.
• What does bromine look like at room temperature?

  It looks like a poisonous red-brown liquid and gives off orange vapour at room temperature.
• What does iodine look like at room temperature?

  It looks like a dark grey crystalline solid giving off a purple vapour when heated.
• What is the chemical test for chlorine gas?

  Damp litmus paper. If chlorine is present, blue litmus paper will be red then bleached white.
• Why does the reactivity of halogens decrease down the group?

  Increasing atomic size means the outermost shell is further away from the nucleus so it is harder to attract another electron.
• What is the reaction of halogens with metals like?

  They will react vigorously to form salts called metal halides.

  Example:

  Sodium + Chlorine ----> Sodium chloride

  2Na Cl2 2NaCl
• What is the reaction of halogens with hydrogen like?

  Hydrogen halides are soluble and dissolve in water to form acidic solutions.

  Example:

  Hydrogen + Chlorine ----> Hydrogen chloride

  H2 Cl2 2HCl
• What are displacement reactions?

  Chemical reactions where a more reactive element displaces a less reactive element from a compound.
• How are displacement reactions examples of redox reactions?

  The halogens gain electrons (Reduction) whilst halide ions lose electrons (Oxidation).
• How to remember redox reactions?

  Oxidation

  Is

  Loss

  Reduction

  Is

  Gain
• Describe a displacement reaction.

  Chlorine water is added to potassium bromide solution, the chlorine will displace the bromine from the salt solution which turns the solution orange.

  Chlorine + Potassium bromide ----> Bromine + Potassium

  Cl2 2KBr Br2 2KCl

  chloride
• Draw a table that shows what would happen if you mixed different combinations of chlorine, bromine and iodine with potassium chloride, bromide and iodide.

  Table:

  
• What are the elements in group 7?

  Fluorine, chlorine, bromine, iodine and astatine.