How would you rank the following elements by increasing electron affinities: F, Cl, Br, I, At ?
Electron affinity increases (that is, it becomes more negative) as you move up through a group. Thus the elements are ranked in increasing electron affinity as follows: At, I, Br, Cl, F. An electron will be more attracted to an orbital that is closer to the nucleus, one that has a higher effective nuclear charge (Z*), than an orbital that is further away from the nucleus. As you see, fluorine does not quite follow the trend. Do not worry about this point for now. Electron affinity decreases (gets closer to zero) as you move towards the left within a period because the charge on the nucleus decreases, resulting in a lower effective nuclear charge, Z*. Electronegativity is very closely related to electron affinity. The difference is that electron affinity involves the attraction of an electron from an infinite distance, whereas electronegativity is a measure of the attractive force between the nucleus and electrons in a bond. Because they are so similar, the factors that affect each of t
