Halogens have ------ electron affinity
The electron affinity of chemical element defines by the number of valence electrons in element’s electronic structure. The maximum amount of electrons in valence molecular orbital is eight and elements aspire to complete their valence shell. By the normal condition, just noble gases have completed valence shell and their electron affinity is zero. In case of halogens, all of them have seven electrons in valence shell, this means that they need just one electron to fill molecular orbital. If we will compare with elements from the group of Carbon, they have 4 electrons and for them it is much complicated to determine, if they need to take or give their electrons to complete valence shell - in both cases it will be 4 electrons that is lead to decreasing of electron affinity. In this way, halogens have positive electron affinity.