The bond enthaply of halogens decreases down the group so why is the reactivity of halogens with hydrogens decreases down the group?

Question

mww · Answer

You will also need to consider the effect of electronegativity. Group VII electronegativity decreases down a group as they pull in electrons less and release less energy in doing so.

faiqraees · Answer

@Photon336 @jhonyy9 @vishweshshrimali5 @ganeshie8 @Directrix @Isaiah.Feynman @IrishBoy123 @inkyvoyd @aaronq @Astrophysics @kropot72

aaronq · Answer

You are talking about the bond enthalpy of diatomic halogen molecules?  And what do you mean by "reactivity of halogens with hydrogens", can you give an example?

mos · Answer

do you mean that the reactivity of hydrohalogens decreases down the group?
HF>HCl>HBr>.... ?

faiqraees · Answer

@aaronq reaction of flourine and hydrogen is much faster than iodine and hydrogen. 
So if in a reaction
H-H+X-X--->2H-X
What role does the bond enthalpy of H-X plays in determining the reactivity?