"The electron affinity is like ionization energy. It is the energy required to add an electron to a neutral atom in the gas phase.

The general trends in EA are hard to
discern

We expect EA to decrease in magnitude
(less negative) down a group as we move further from the nucleus. Only observed for Groups 1 and 8, or elements after Ne.

We expect EA to increase (more negative) across a row as the nuclear charge increases and size decreases. There are plenty of exceptions to this"