- reactivity, electronegativity, mpt, bpt, all increase up the group because the ionic radius is smaller up the group, as there is less shielding, so the attraction between the electrons and nucleus will be stronger towards the top
- the solubility increases up the group because they are more electronegative and polar, so can overcome the forces of the hydrogen bonds in water. note that fluorine also exhibits hydrogen bonding.
- they look darker and become more volatile down the group, this is because there will be more electrons in the elements towards the bottom, so they will have stronger intermolecular forces. this is why iodine is a solid, bromine, a liquid, and chlorine and fluorine are gases.
- become stronger reducing agents as you go down
- with hydrogen H2 + X2 —-> 2HX
chlorine needs dark
bromine needs a platinum catalyst at high temperature
iodine needs a platinum catalyst at a high temperature
- hydrogen halide + ammonia gas —-> ammonia halide
- halogen + sulphuric acid ——> hydrogen halide (they are oxidised)
chlorine= steamy fumes (HCl)
bromine= misty fumes and red/ brown vapour (HBr)
iodine= violet fumes (HI)
- potassium halide + Cl2 —-> potassium chloride + halogen
- disproportionation reactions with alkali
add dilute nitric acid and aqueous silver ammonia.
- chlorides= white ppt
- bromides = cream ppt
- ioides = pale yellow ppt
to that ppt, add dilute, then concentrated ammonia
- AgCl= dissolves in dilute ammonia
- AgBr= only dissolves in concentrated ammonia
- AgI = does not dissolve in any