Re: Why is bromine more reactive than chlorine?

The general rule of thumb of reactivity on the perodic table is left and 
down is more reactive, and right and up is least with francium being the 
most reactive and helium being the least.  This is do to the shielding 
effect the closest electrons have on the necleus and this weakens the bond 
that the protons have on the electrons.  Bromine has the same amount of 
valence electrons (7) as chlorine, however there is more shielding effect 
because the bromine is just a bigger atom.  All reactivity refers to is the 
willingness an atom has to gain or lose electons.  A highly reactive 
element will give up atoms more "easily" than a less reactive element.  

I hope this answers you question.
Late
R Weiner