Is this a good alternative definition of electron affinity?

[sneakycooky]

TL;DR

electron affinity (traditional definition): the amount of energy released by an element in its gas form when gaining an electron

second definition?: the stability gained by an element in its gas form when gaining an electron

Is this a correct definition?

traditional definition of electron affinity: the amount of energy released by an element in its gas form when gaining an electron

second definition?: the stability gained by an element in its gas form when gaining an electron (e.g. halogens are more stable after gaining an electron, and when gaining an electron, the system [i.e. electron + atom] loses energy, thus becoming more stable)

reasoning: losing energy is highly associated with gaining stability (I think they are two sides of the same thermodynamic concept)

Is this an acceptable alternative definition? From a distance it looks okay, but I am often wrong about such things.

 

[etotheipi]

I'm by no means an authority, however I wouldn't say the second definition is sufficient.

The electron affinity, $E_{ea}$, is a numerical quantity - the energy released per mole on gaining an electron. As such, the definition must be precise.

Granted, the atom-electron system becomes more energetically stable after the first electron affinity. But this is more of a consequence, and not the definition of $E_{ea}$.

As an aside, it might be worthwhile to make the distinction between $E_{ea}$ and the enthalpy change of electron capture ionisation. $E_{ea}$ is the energy released, whilst the enthalpy change is a change in the total energy. Assuming constant pressure and volume, $\Delta H_{ea} = - E_{ea}$.

 

[sneakycooky]

I'm by no means an authority, however I wouldn't say the second definition is sufficient.

The electron affinity, $E_{ea}$, is a numerical quantity - the energy released per mole on gaining an electron. As such, the definition must be precise.

Granted, the atom-electron system becomes more energetically stable after the first electron affinity. But this is more of a consequence, and not the definition of $E_{ea}$.

As an aside, it might be worthwhile to make the distinction between $E_{ea}$ and the enthalpy change of electron capture ionisation. $E_{ea}$ is the energy released, whilst the enthalpy change is a change in the total energy. Assuming constant pressure and volume, $\Delta H_{ea} = - E_{ea}$.

Interesting. I think I agree with you; the trend of increasing the system's stability upon gaining an electron does exist, but it is much more difficult to measure; the more precise measurement makes for a better definition. I am glad that the trend actually exists, as it does help my understanding of the concept.
Thanks for your input!

 

[mjc123]

First, to be pedantic, the electron affinity refers to an atom of the element. E.g. the electron affinity of chlorine relates to the reaction Cl(g) + e → Cl^-(g). Talking of "an element in its gas form" might suggest the participation of Cl₂(g).

Second, "stability" is a woolly concept, by no means equivalent to the negative of energy. You always have to ask: stability with respect to what?
For instance, the second electron affinity of oxygen is negative; that is, O^2- is unstable relative to O^- + e in the gas phase. Yet we can form many oxides, containing the O^2- ion and not O^-. This is because the extra energy put into create O^2- is more than compensated for by the lattice energy of the ionic solid containing O^2-, so the overall process is favourable.