Which Ion Has a More Negative Electron Affinity: Na+ or Cl?

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Discussion Overview

The discussion revolves around the concept of electron affinity, specifically comparing the electron affinities of Na+, Na, and Cl. Participants explore the theoretical implications and reasoning behind the electron affinity values of these ions and atoms.

Discussion Character

  • Homework-related
  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant suggests that Na has a greater negative electron affinity than Na+ because adding an electron to Na would result in paired electrons in the s orbital, while Na+ already has a noble gas configuration.
  • Another participant proposes analyzing the problem using electrostatic principles, questioning whether it is easier to attach an electron to neutral Na or to positively charged Na+.
  • A different participant asserts that electron affinity is inversely proportional to atomic radius, raising questions about the relationship between atomic radius and positive charge.
  • One participant clarifies a misunderstanding regarding the comparison of Cl and Cl-, emphasizing that the original question was about Na+ and Cl, and discusses the implications of electron transfer between these species.
  • Another participant notes that atoms tend to seek the electronic configuration of the nearest noble gas, suggesting that Na+ seeks Ne and Cl seeks Ar.

Areas of Agreement / Disagreement

Participants express differing views on the electron affinities of Na+, Na, and Cl, with no consensus reached on which has a more negative electron affinity. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Some participants' arguments depend on assumptions about atomic structure and electrostatic interactions, which may not be universally accepted. The discussion includes references to electron configurations and the behavior of ions in reaction media, but these are not fully explored or agreed upon.

Who May Find This Useful

This discussion may be useful for students reviewing concepts in general chemistry, particularly those interested in electron affinity and atomic interactions.

OneMan98
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Hi guys, my first post/question. Excuse my stupidity if you think this is an easy question, I'm really having a difficult time with reviewing this part in general chemistry.

Homework Statement


Which has a more negative electron affinity, Na+ or Na? Na+ or Cl?


2. The attempt at a solution
My thinking was to write down the ground-state electron configurations.

Na+: [Ne]
Na: [Ne]3s^1
Cl: [Ne]3s^2 3p^5

Electron affinity is described as the energy change that occurs when an electron is added to an isolated atom in its gaseous state.

I assumed for the first part of the question that Na had a greater negative electron affinity because it would become paired in the s orbital, and since Na+ already has a noble gas configuration, wouldn't adding an electron make the Electron affinity positive?

For the second part I naturally assumed it was Cl for similar reasons, and since the textbook says halogens have the greatest Electron affinities.

Answer for both questions: Na+

I don't really understand how/why, so if someone could please explain in a manner that's simple yet concise, that would be awesome.

Thanks Physics forum! I look forward to being an active member on here and learning a lot.
 
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I think you should try to analyze it just taking simple electrostatic into account.

What is the electron charge?

What should be easier - attaching electron to neutral Na or to positively charged Na+?

What should be easier - attaching electron to neutral Cl or to negatively charged Cl-?
 
man WOW! it's much simpler
electron affinity is inversly propertianal to atomic radius RIght? why?
and atomic radius is directly proportianal to number of positive charges right? why?
 
Borek said:
What should be easier - attaching electron to neutral Cl or to negatively charged Cl-?
I think you misread the second question. It was "Na+ or Cl?", not "Cl- or Cl?".

Na+ or Cl is pretty easy to answer by considering what happens if you have an Na+ ion and a Cl atom fight over an electron. If the Na+ ion gets it, you end up with an Na atom and a Cl atom. If the Cl atom gets it, you end up with an Na+ ion and a Cl- ion. If you look around you, you will see Na+ and Cl- ions all over the place, happily bumping into each other. I defy anyone to find elemental sodium metal and chlorine gas in peaceful coexistence.
 
well, that in case they ARE in the same reaction medium
but it's still right because any atom wants to get the electronic confugaration of the nearest noble gas so for Na it's Na+ Ne and for Cl its Cl- Ar
 

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