Ionization and electron affinity

Click For Summary

Discussion Overview

The discussion revolves around the concepts of ionization energy and electron affinity, particularly focusing on the apparent contradiction regarding energy requirements for adding and removing electrons from atoms and ions. Participants explore the definitions, conventions, and implications of these terms in the context of neutral atoms and anions.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants express confusion about why energy is required to remove an electron (ionization energy) after energy is required to add an electron (electron affinity), questioning if this violates conservation of energy.
  • One participant notes that the energy for adding an electron to a neutral atom and removing it from an anion are of equal absolute value but opposite sign, highlighting the importance of understanding the conventions used in data tables.
  • Another participant reiterates the confusion about energy requirements, suggesting that adding an electron should release energy rather than require further energy for removal.
  • It is mentioned that ionization energy is always positive for neutral atoms, while electron gain enthalpy can be either negative or positive.
  • Some participants clarify that the concept of ionization energy typically refers to neutral atoms, not anions, and question the implications for anions.
  • One participant seeks sources to support the claim that ionization energy for anions might be negative, indicating a lack of consensus on this point.
  • Another participant provides a link to a Wikipedia article defining ionization energy, reinforcing that it generally pertains to neutral atoms.
  • Discussion includes the clarification that successive ionization energies refer to removing electrons from ions, not neutral atoms.
  • Participants provide chemical equations to illustrate the relationships between electron affinity and ionization energy.

Areas of Agreement / Disagreement

Participants generally agree on the definitions of ionization energy and electron affinity but express disagreement and confusion regarding the implications for anions and the energy dynamics involved. The discussion remains unresolved regarding the specific energy requirements for ionization in the context of anions.

Contextual Notes

There is a noted dependence on definitions and conventions used in the discussion, particularly regarding the signs of energy values associated with ionization and electron affinity. Some assumptions about the behavior of anions and the implications of energy requirements remain unresolved.

harman90
Messages
22
Reaction score
0
I am confused about Ionization and electron affinity concept

If energy is Required to add the electron to gaseous atom (Electron affinity - in case of noble gases) Then why further energy is required to Remove it? (Ionization energy)
isnt this violation of Conservation of energy?
 
Physics news on Phys.org
The energy for the addition of an electron to a neutra gas atom and that for the removal of an electron from an anion are of equal absolute value but opposite sign.
However there is much confusion as the tabulated electron affinity often refers to the second formulation, i.e. the energy required to remove an electron from an anion.
So you must be very careful about which convention is used in the table of data you are consulting.
 
sorry My question is : (leaving the sign conventions aside)
If energy is Required to add the electron to gaseous atom (Electron affinity) Then why further energy is required to Remove it? ( infact it should release the energy)
 
harman90 said:
sorry My question is : (leaving the sign conventions aside)
If energy is Required to add the electron to gaseous atom (Electron affinity) Then why further energy is required to Remove it? ( infact it should release the energy)
You are completely right. Who claimed the opposite?
 
Thank you for reply.
Well, it is well known fact that Ionization energy (second case) is always positive I.e Energy is required to Remove the electron.

(electron gain enthalpy can be negative or positive, but Ionization enthalpy is always positive)
 
That's only true for the ionization of neutral atoms, not for the ionization of anions.
 
So it means , In case anions, IE is negative ?

I can't find any link favouring that statement ? Can you give me any source ?
 
https://en.wikipedia.org/wiki/Ionization_energy
sais
"The ionization energy (IE), (or "ionization potential" - not recommended),[1] is qualitatively defined as the amount of energy required to remove an electron from an atom or molecule in the gaseous state."
So the term ionization energy usually refers to the ionization of a neutral atom or molecule, not an anion. This is also what I remember.
 
2nd Ionization enthalpy... is actually removing electron from the ION.

infact all the successive Ionization energies are for Removing electrons from Ions.
 
Last edited:
  • #10
That's why they are explicitly called second IEs.
 
  • Like
Likes   Reactions: harman90
  • #11
If X is neutral :

X + e- + E.A. -----> X- : E.A. is the electron affinity.
X+ I. E. ---> X+ + e- : I.E. Ionization energy
X+ + 2nd I.E. -----> X2+ + e-
 
  • #12
Thank you very much ... It makes sense now.
 

Similar threads

Replies
1
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
Replies
2
Views
3K
  • · Replies 12 ·
Replies
12
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 0 ·
Replies
0
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K