Question

Chlorine, Bromine and Iodine all react with hydrogen. (i) State the trend in the reactivities of the halogens with hydrogen. (ii) Explain the trend in terms of bond energies.?

Answer 1

i.

Chlorine is most reactive with hydrogen, followed by bromine and then iodine. This shows that reactivity of halogens decreases down the group.

ii.

This is because the number of outer shells increases down the group, increasing the distance of the electrons from the nucleus, making the attraction between the electrons and nucleus weaker. This results in electrons being less easily gained down the group, hence reactivity decreases down Group VII.