The Halogens Flashcards
what type of molecules do the halogens exist as?
diatomic molecules
what happens to the boiling point of halogens when you go down the group?
boiling point increases
why does the boiling point increase as you go down group 7?
- the number of electrons increases as you go down the group
- there are stronger London forces as you go down the group
- more energy is required to overcome the intermolecular forces
what is the outer shell electron configuration of halogens?
s2, p5
are halogens reduced or oxidised?
reduced, gains one electron to form 1- ions
what is the trend in reactivity down group 7?
reactivity decreases
why does reactivity decrease as you go down group 7?
- atomic radius increases
- electron shielding increases
- nuclear attraction weakens
- greater nuclear charge
- harder to gain one electron
what are displacement reactions?
when the most reactive halogen replaces the least reactive halogen in a reaction
what is a disproportionation reaction?
a redox reaction in which the same element is both oxidised and reduced
what are some examples of disproportionation reactions?
- the reaction of chlorine and water (used in water treatment)
- the reaction of chlorine with cold, dilute aqueous sodium hydroxide (used to form bleach)
what is the equation for the reaction of chlorine and water?
Cl2(aq) + H2O(l) - >HClO(aq) + HCl(aq)
what is the equation for the reaction of chlorine with cold, dilute aq NaOH?
Cl2(aq) + 2NaOH(aq) -> NaClO(aq) + NaCl(aq) + H2O(l)
what are the benefits of chlorine use?
killing bacteria in water treatment
what are the risks of chlorine use?
- extremely toxic gas
- chlorinated water reacts with organic hydrocarbons (from decaying vegetation) forming chlorinated hydrocarbons = suspected of causing cancer
what colour and state is flourine?
- gas
- yellow
