Question

Why do the halogen atoms have the greatest electron affinity?

Answer 1

The amount of energy released when an electron is connected to a neutral atom or molecule in the gaseous state to produce a negative ion is described as the electron affinity (${{E}_{ea}}$) of an atom or molecule. This is not to be confused with the enthalpy change of electron capture ionisation, which is negative when energy is released. In other words, there is a negative difference between this enthalpy change and the electron affinity.

Complete answer:
We should be aware that electron affinity for any element is determined by parameters such as the amount of protons present and the atom's size. We can see that as we move from left to right along a period in the periodic table, electron affinity rises, but as we move down the group, electron affinity decreases. When compared to other groups in the periodic table, halogens have the highest electron affinity. This is owing to the tiny size of all halogen atoms and the nucleus's high effective nuclear charge.
Chlorine draws additional electrons the most strongly, whereas neon attracts them the least. Because the electron affinities of noble gases have not been definitively determined, they might have slightly negative values. Prior to reaching group 18, ${{E}_{ea}}$ usually increases over a period (row) in the periodic table. This is due to the atom's valence shell filling; when a group 17 atom gains an electron, it releases more energy than a group 1 atom because it receives a filled valence shell and is therefore more stable. The valence shell is complete in group 18, thus any additional electrons are unstable and tend to be expelled soon.
The capacity of an atom to receive an electron is measured by electron affinity. The halogens, which belong to Group VIIA, have the highest electron affinities because adding an electron to an atom results in a totally filled shell.
Hence halogens have the greatest electron affinity.

Note:
The electron affinity can become negative in certain conditions. Negative electron affinity is frequently needed in order to produce efficient cathodes capable of supplying electrons to the vacuum with minimal energy loss. With band diagrams in which the electron affinity is one parameter, the measured electron yield as a function of different factors such as bias voltage or lighting conditions may be utilised to explain these structures.