Why is electron affinity negative? An electron carries energy so if we had an electron doesnt that mean we add energy? Please describe in a non-PhD lingo that a first semester chem student can comprehend.
The electron affinity is the energy released when an electron attaches to an atom in gas phase. The sign of the energy depends on the convention used in the textbook. For instance, in Atkins' Physical Chemistry textbook it is defined as a positive quantity which means that the process is exothermic. However, if your point of view is the potential of the system as mention in the comments by Avnish Kabaj then you will have your negative electron affinity since the reference energy is zero when the electron is far from the gas phase atom and when it is brought close to the atom the final potential energy is negative.