How does the electronegativity of the halogen atom change as group 7 is descended?

Electronegativity is the measure of how strongly an atom attracts a bonding pair of electrons to itself. As group 7 is descended, the electronegativity decreases. This is because the size of the halogen atom increases down the group, meaning there is increased electron shielding. Therefore, the nucleus of halogen atoms lower down group 7 (eg. bromine) is further away from the bonding electrons; this reduces the attraction between the nucleus and the electrons, thus decreasing electronegativity.