In chemistry, electron affinity refers to the energy change that occurs when an atom or molecule gains an electron to form a negatively charged ion. The process of electron affinity involves the attraction between the incoming electron and the nucleus of the atom.
Energy is released during electron affinity because the added electron occupies an orbital that is closer to the nucleus than the previous occupied orbitals. As the electron approaches the nucleus, it experiences an attractive force from the positively charged protons in the nucleus. This attraction leads to a decrease in potential energy.
According to the laws of physics, when an object or system decreases its potential energy, it releases energy into its surroundings. In the case of electron affinity, this energy is typically released in the form of heat or light, depending on the specific circumstances.
It's important to note that not all atoms or molecules have a favorable electron affinity. Some may have a positive electron affinity, meaning that energy is required to add an electron to form an ion. In such cases, the process is endothermic, and energy must be supplied to overcome the repulsive forces between the negatively charged electron and the negatively charged ion.