group 7 ( halogens )

• what elements are in group 7 ?

  • fluorine , chlorine , bromine , iodine , astatine
• how many electrons does group 7 have in their outer shell ?

  • 7
• what do halogens exist as ?

  • diatomic molecules ( cl2 , Br2 , i2 )
• in diatomic molecules how do both atoms end up with an outer shell ?

  • they share one pair of electrons in a covalent bond - gives both outer shell
• what happens when you go down group 7 ?

  • the melting and boiling points increase
• what is chlorine at room temperature ? ( cl2)

  • fairly reactive , poisonous , green gas
• what is bromine at room temperature ?

  • poisonous red brown liquid - which gives off an orange vapour
• what is iodine at room temperature ?

  • a dark grey crystalline solid which gives off a purple vapour when heated .
• using trends in physical properties of halogens predict how astatine is at room temperature ?

  • dark coloured solid
• what is the trend in physical properties as you go down group 7 ?

  • the melting point increases and the colours of the halogens gets darker
• how do u test to see if a gas is chlorine ?

  • holding a piece of damp blue litmus paper over it
  • chlorine will bleach the litmus, turning it white
• why might litmus paper turn red before it turns white when testing for chlorine ?

  • because a solution of chlorine is acidic
• what happens when a halogen atom gains one electron ?

  • it forms a 1- ion with a stable electron structure ( full outer shell )
• how do you determine how reactive the halogen is ?

  • the easier it is for a halogen atom to attract an electron , the more reactive it is .
• what happens to the reactivity as you go down group 7 ?

  • the halogens become less reactive
• why do halogens become less reactive as you go down group 7 ?

  • it gets harder to attract the extra electron to fill the outer shell when its further away from the nucleus .
• what is a metal halide ?

  • a salt that's formed when halogens react with some metals
• why are the halogens higher up in group 7 more reactive ?

  • they can attract the outer electron of the metal more easily
• what is formed when halogens react with hydrogen ?

  • hydrogen halides
• are hydrogen halides soluble or insoluble ?

  • soluble - they dissolve in water to form acidic solutions
• why can you use the reactions of chlorine , bromine and iodine to predict ho fluorine and astatine will react ?

  • because they all have the same number of electrons in their outer shell so the reactions are all similar
• why type of reaction are the halogen displacement reactions ?

  • redox reactions
• what happens in a halogen redox reaction ?

  • the halogens gain electrons (reduction) and the halide ions lose electrons (oxidation)