Question

Define The electronic affinity

Answer 1

The electronic affinity, sometimes referred to as AE, A or eA, is the amount of energy released as a result of the capture of an electron by an isolated atom. The greater the electron affinity, the more the capture of an electron by the atom releases energy and the more the resulting negative ion is stable. A negative electron affinity means, on the contrary, that it would be necessary to supply energy to the atom in order to attach an electron to it.

This energy, normally measured in units of frequency or wave number and translated into eV (but already at the cost of a loss of precision) in the atomic physics experiments which give the most accurate values, is often reported in KJ / mol in chemical works. From a thermodynamic point of view, electronic affinity is the enthalpy variation, ?H, of the electron capture reaction. If the element picks up the electron and produces an energy release, the reaction is exothermic and ?H is assigned a negative sign. However, there is a convention according to which the electronic affinity values ??are given in absolute value (as in the table infra). According to this convention, the higher the electronic affinity value, the more the element is a good electron sensor.


To give meaning to this magnitude, it must not be forgotten that the atom X and the ion X - are supposed to be isolated, in the gas phase. This magnitude is therefore more useful in theoretical cycles such as the Born-Haber cycle, than to predict, experimentally, reactions taking place, for example, in the aqueous phase.

The energy released during the capture of a first electron by the element under consideration is called the first electronic affinity. The energy released during the capture of a second electron is called the second electron affinity and so on.

In general, for an element X, the reaction associated with the electronic affinity is:

${ X _ {(g)} + e ^ {-} \rightarrow X _ {(g) } ^ {-}}$ (1st electronic affinity)

${ X _ {(g)} ^ {-} + e ^ {-} \rightarrow X _ {(g) -} \ rightarrow X _ {(g)} ^ {2-}}$ (2nd electronic affinity)

Answer 2

The energy released when an electron is added to its  outer most cell is known as electron affinity