It is possible to add an electron to any atom, ion or molecule. The electron affinity of an atom is defined as the amount of

                                                     X(g) + e^- →  X ^-(g) + Energy

energy released when an electron is added to a neutral gaseous atom. For example, the electron affinity of a H atom is -72.8 K J mol^-1, i.e. 72.8 k J are released when 1 mol of  H atoms combine with 1 mole of electrons to give 1 mole of H^- ions. The greater the electron affinity, the more negative is the  ΔE value and greater is the energy released. Halogens form very stable halide ( X ^- ) ions, so large amount of energy is released and  ΔE values are negative. Electron affinity values are more difficult to determine directly but are calculated indirectly values are negative. Electron affinity allures are more difficulty to determine directly but are calculated indirectly using Born-Haber cycle.

For more help in Electron Affinity click the button below to submit your homework assignment