Hello …...

The increasing order of reactivity among group 1 elements is liCl>Br>I . Explain .

in grp17 , as we move down the group , the electronegativity becomes less negative -, its tendency to gain electron will decrease down in grp 17 , thus reactivity decrease as we move down the group . 
the electron gain enthalpy of f is less negative than cl , still its the most reactive halogen . due to bond dissociation enthalpy . 
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