Electron affinity and electron gain enthelpy

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Discussion Overview

The discussion centers on the terms "electron affinity" and "electron gain enthalpy," specifically exploring their definitions and the differences between them. The scope includes conceptual clarification and technical explanation related to thermodynamic properties in chemistry.

Discussion Character

  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant seeks clarification on the difference between electron affinity and electron gain enthalpy, noting both seem to describe the same enthalpy change process.
  • Another participant asserts that electron affinity refers to the energy difference between an atom and its ion after gaining an electron, suggesting it is not an enthalpy measurement.
  • A participant references a source that states electron affinity is numerically equal to the negative of electron gain enthalpy, which adds to the confusion regarding the terms.
  • One participant points out that electron affinities are definitively energy differences, not enthalpy differences, while noting the numerical difference between the two is small.
  • A later reply indicates that the confusion has been resolved among participants.

Areas of Agreement / Disagreement

Participants express differing views on whether electron affinity and electron gain enthalpy are the same or different, with some asserting they are distinct while others reference sources that suggest a numerical relationship. The discussion remains somewhat unresolved regarding the definitions and implications of the terms.

Contextual Notes

There are limitations in the definitions provided, as participants rely on different sources and interpretations of the terms, which may depend on specific contexts or conventions in chemistry.

Zatman
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Hello,

I was wondering if someone might be able to explain these terms. Specifically, the difference between them. From what I have read they seem to describe the same thing, i.e. the enthalpy change involved in:

X(g) + e- → X-(g)

I am sure there is a difference that I am just not understanding. Any help would be appreciated.
 
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I have never run before into the term electron gain enthalpy, but electron affinity refers really to the energy (not enthalpy) difference between an atom and an ion (+electron) in vacuum.
 
Hmm. Well I've read the following which confused me:

"The tendency for atoms of neutral elements to gain electrons is measured by the electron affinity. This is numerically equal to the negative of the electron gain enthalpy, which is the enthalpy change when a gas-phase atom gains an electron."

[Foundations of Inorganic Chemistry, MJ Winter and JE Andrew, p8]
 
So...what's the mystery? It's something that these guys are defining as the negative of the EA.
 
Right, confusion gone. Thanks guys!
 

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