1: Electronaffinity refers to the act of acquiring an electronic …..
The halogens are eager to accept an electronic to create a stable noble-gas electronic configuration
Therefore, halogens are high in electron affinity…
2:. 2:. If a halogen gains an electron, it becomes stable as it now has its orbitals, octet and is more stable. This is why the 1st EA has a large size.
However, if you want an electron to be added, it must go to a new energy level. This will not be good for the electronic structure of your atom. The difference in the potential or electric stability formed is therefore almost 0. The halide ion is almost zero in terms of its electric stability or potential formed.
You can think of it this way: The 2nd EA for a halide is roughly the same as its 1st Ionization Energy of the alkali metallic to which it’s isoelectronic (since adding or removing an electron will release as much energy). Because the electron is so far away from the nucleus that the 1stIonization energy of Group 1 metals is usually very low, so is their 1st electron affinity.
Additionally, the halogen now has a negative charge and experiences repulsion from the electron that will soon be added.