Question

What are the periodic trends in electron affinity?

Answer 1

Hint: Periodic trends are distinct patterns in the characteristics of chemical elements that may be found in the periodic table. Electronegativity, ionisation energy, electron affinity, atomic radii, ionic radius, metallic character, and chemical reactivity are all major periodic patterns. Changes in the atomic structure of chemical elements within their respective periods (horizontal rows) and groups in the periodic table cause periodic trends. Based on their atomic structures and characteristics, these rules allow the chemical elements to be arranged in the periodic table. The unknown characteristics of any element might be partially known due to periodic patterns.

Complete answer:
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.
 $ X\left( g \right)\text{ }+\text{ }{{e}^{-}}~\to \text{ }{{X}^{-}}\left( g \right)\text{ }+\text{ }energy $
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.
Down a group
As the electron affinity diminishes, the following happens:
More energy levels are added to the atom as you travel down a group. $ {{E}^{-}} $ go away from the nucleus as much as possible. As a result, components near the bottom of a group do not attract other $ {{e}^{-}} $ as strongly as those at the top.
As nuclear shielding improves, the appeal of new $ {{e}^{-}} $ becomes less appealing.
The nuclear charge decreases as you go down a group, increasing the nucleus's attraction for additional $ {{e}^{-}} $ ; nevertheless, the greater nuclear shielding compensates for this. It reduces the nucleus's attraction to other $ {{e}^{-}} $ .
Across a period
The affinity for electrons grows:
There are no new energy levels added to the atom throughout time.
From Left to Right, the e- arrangement approaches a stable octet:
When atoms reach their stable octet, they release more energy.
The nuclear shielding remains unchanged (i.e., there are no additional inner $ {{e}^{-}} $ shells to protect outer $ {{e}^{-}} $ from the positive nucleus' attraction).
Because of the higher nuclear charge, electrons are kept closer to the nucleus from left to right. As a result, electrons are attracted to them more strongly.

Note:
Despite the fact that $ {{E}_{ea}} $ has a wide range of properties across the periodic table, some trends emerge. Nonmetals, on average, have a higher positive $ {{E}_{ea}} $ than metals. Atoms with more stable anions than neutral atoms have a higher $ {{E}_{ea}} $ . 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.