Group 7

• how do halogens exist at room temperature ?

  diatomic molecules
• do halogens exist in their elemental form in nature ?

  no
• on earth how do halogens exist as ?

  stable halide ions (eg Cl- )dissolved in sea water or combined with sodium or potassium (NaCl)
• does group 7 contain metals in all physical states ?

  yes solid liquid and gas
• Does the boiling point in halogens increase or decrease ?

  Increases as when you go down the group there are more electrons so there are more stronger london forces which means more energy is needed too break the intermolecular forces which increases the boiling point.
• how many electrons are on the outer shell of halogens ?

  7
• how many electrons are in the s sub shell and the p outer sub shell

  2 = s

  5 = p
• what is the most common type of reaction for a halogen ?

  redox
• is a halogen reduced or oxidised ?

  reduced by gaining 1 electron to form a 1- ion with a full outer shell
• why are group 7 elements called oxidising agents ?

  the other species looses electrons to halogens and so halogens help other species get oxidised
• write the redox reaction for chlorine ?

  Cl2 + 2e- --> 2Cl-
• does reactivity increase or decrease as you go down group 7?

  decreases
• what type of reaction is able to show reactivity ?

  disolacement reaction with halide ions
• Why does reactivity decrease as you down group 7?

  the atomic radius increases and so there are more inner shells between the nucleus and outermost shell which increases shielding. This means there is less attraction to capture an electron from another species and a halogen wants to gain an electron unlike a group 2 metal and so the reactivity decreases whereas for a group 2 metal it increases
• as you go down group 7 does the oxidising agents becomes stronger or weaker ?

  weaker
• if an aqueous solution of chlorine is added to bromine what colour will form ?

  orange colour from bromine forming

  Cl2 (aq) +2Br- (aq) --> 2Cl- (aq) + Br2 (aq)
• if an aqeous chlorine solution reacts with iodine what colour forms ?

  violet colour from idodine forming

  Cl2 (aq) _ 2I- (aq) --> 2Cl- (aq) + I2 (aq)
• what happens when bromine reacts with chlorine ?

  no reaction
• what happens when bromine reacts with iodine ?

  Violet colour from iodine

  Br2 (aq) + 2I- (aq) --> 2Br- (aq) + I2 (aq)
• what happens when iodine solution reacts with chlorine ?

  no reaction
• what happens when iodine solution reacts with bromine ?

  no reaction
• what colour is chlorine in water ?


  pale green
• what colour is bromine in water ?

  orange
• what colour is iodine in water ?

  brown
• what colour is chlorine is cyclohexane ?


  pale green
• what colour is bromine in cyclohexane ?

  orange
• what colour is iodine in cyclohexane ?

  violet
• why do we have to do a test in cyclohexane ?

  it is hard to tell between iodine and bromine in water depending on concentration as so using a non polar solvent like cyclohexane allows the non polar halogens to dissolve more readily allowing it to be easier to distinguish colours
• what is the equation of chlorine with bromide ions ?

  Cl2 (aq) + NaBr (aq) --> 2NaCl (aq) +Br2 (aq)

  Cl2 (aq) +2Br- (aq) --> 2Cl-(aq) +Br2(aq)

  0 --> -1 reduction

  -1 --> 0 oxidation
• what is colour of fluorine ?

  pale yellow gas reacting
• is fluorine reactive ?

  yes it reacts with almost anything it comes into contact with
• talk to me about astatine ?

  extremly rare as its radioactive and decays rapidly so it hasnt been seen before
• what is a disproportionate reaction ?

  a redox reaction where the same element is both oxidised and reduced
• write the disproportionate reaction of chlorine with water ?

  Cl2 (aq) + H20 (l) --> HClO (aq) + HCl (aq)

  0 --> -1

  0 --> +1

  chlorine is both reduced and oxidised
• what is chlorine used as ?

  water disinfectant as it kills harm full bacteria
• what are the products of using chlorine with water ?

  HCl and HClO
• what kills the bacteria ?

  the chloric acid (l) in HClO and chlorate ions
• what does chloric acid also act as ?

  weak bleach
• what is the reaction of chlorine with cold dilute NaOH ?

  Cl2(aq) + 2NaOH (aq) --> NaClO (aq) + NaCl (aq) +H2O (l)

  0 --> -1

  0 --> +1
• what does the resulting solution of chlorine with NaOH have ?

  large amounts of chlorate ions ( ClO -) ,ions from sodium chlorate (NaClO)

  this solution is present in household bleach