Explain why the 2nd Electron aiffinity of Chlorine is Endothermic whilst the first electron affinity is exothermic

With the first electron affinity, the chlorine atom is one electron from a full octet ( and is a neutral species). When you add an electron to the chlorine, the negatively charged electron is electrostatically attracted to the positive charge of the nucleus. This results in the release of heat energy,(exothermic process) In contrast, when you are adding the second electron (2nd electron aiffinity) this time you are adding a negatively charged electron to a negative ion. This results in repulsion, you need to put in energy to overcome the repulsive forces, resulting in the process being endothermic