[magicalatom]

which of the following is most likely to undergo reduction?

A.Cl2
B. Cl-
C. Na
D. Na+
E. both Cl- and Na+

Answer was A in both editions of text.

I chose D because more positive it would want to gain, hence the term reduction is to gain electrons, but why is it Cl2?  charge of Cl2 is zero, yes.  There is something I am missing here, some concept.  Does anyone see why it is choice A?

[clinz63]

You have to remember why atoms/ions undergo oxidation or reduction. It is to achieve an octet state (a noble gas state) because it is stable. Your answer, Na⁺ has the electronic configuration 1s²2s²2p⁶ or [Ne]. Therefore, it is stable.

One of the choices is not in a noble gas consideration but if you consider the quickest way to a noble gas configuration, it is not reduction.

Cl₂ on the other hand has an octet configuration but it is by a covalent bond. Meaning, the eighth valence electron is being shared between the two Cl atoms. Now, what would make these Cl atoms more stable than a shared octet state?

[magicalatom]

But Na+ sodium configuration is the whole configuration then 3s1   Wouldn't it have to lose one more electron to become Ne configuration?

You have to remember why atoms/ions undergo oxidation or reduction. It is to achieve an octet state (a noble gas state) because it is stable. Your answer, Na⁺ has the electronic configuration 1s²2s²2p⁶ or [Ne]. Therefore, it is stable.

One of the choices is not in a noble gas consideration but if you consider the quickest way to a noble gas configuration, it is not reduction.

Cl₂ on the other hand has an octet configuration but it is by a covalent bond. Meaning, the eighth valence electron is being shared between the two Cl atoms. Now, what would make these Cl atoms more stable than a shared octet state?

[magicalatom]

This is a nice site:
http://www.chemguide.co.uk/atoms/properties/ionstruct.html

So I see Na is indeed 3s1, but Na+ I need to remove one electron so 2p6 same as Ne.  Okay I see how they do this.  Okay so now I see why it is Cl2, but can you elaborate a little more on Cl?  I know Cl has a minus one charge.  Is this a way to look at it if one of the Cl took octet then the other Cl would be 3s2 3p4  so it would be 2 electrons in the whole so +2 so it would be the answer choice that wants to be reduced the most from all the other choices. 

Did I make any sense here?  I feel I got it.  Thanks.

PS:  Even easier answer now I see is atoms hate sharing just like two year olds hehe

[clinz63]

You could say that but that doesn't really happen because the electron is equally shared between the two kids, I mean chlorine atoms. So the chlorine atoms would be more stable if they each had a toy, I mean electron.

[magicalatom]

So what if there were two choices such as Cl2 and I2 and or Br2   how would we pick one from these that would want to be reduced the most?  I would say the trend for top to bottom on the periodic table of elements the lower we go the more the atom is stable because of the radius and less electronegativity so I would say Cl2 would be the one that wants to be most reduced.

Am I correct?

[Enthalpy]

You have to remember why atoms/ions undergo oxidation or reduction. It is to achieve an octet state (a noble gas state) because it is stable. Your answer, Na⁺ has the electronic configuration 1s²2s²2p⁶ or [Ne]. Therefore, it is stable.

That's oversimplified.

If you have atoms and ions alone in vacuum, any Na⁺ meeting a lone electron will immediately make an Na atom, releasing much energy. Lone ions are not stable. You won't meet them alone at room temperature.

Ions exist (...with some heavy interpretation needed!) in solids and in solutions, only where one or rather several ions of opposite charge, or atoms with partial charge, are immediate neighbours of the ion. Then, the electron movement that creates these "ions" is extremely short, far less than an atom's size, and gets energetically possible.

So when telling "ion" one should know whether in a solid, a plasma, or in a solvent and which one.

[magicalatom]

That is why I chose Na+ as answer but it was wrong.  The answer was Cl2 and I suppose it is because without sharing it makes atoms unstable.  I am still sort of confused on the answer choice and even further trying to figure out what if they had Br2 or I2 in the choices which one would it ben then?

You have to remember why atoms/ions undergo oxidation or reduction. It is to achieve an octet state (a noble gas state) because it is stable. Your answer, Na⁺ has the electronic configuration 1s²2s²2p⁶ or [Ne]. Therefore, it is stable.

That's oversimplified.

If you have atoms and ions alone in vacuum, any Na⁺ meeting a lone electron will immediately make an Na atom, releasing much energy. Lone ions are not stable. You won't meet them alone at room temperature.

Ions exist (...with some heavy interpretation needed!) in solids and in solutions, only where one or rather several ions of opposite charge, or atoms with partial charge, are immediate neighbours of the ion. Then, the electron movement that creates these "ions" is extremely short, far less than an atom's size, and gets energetically possible.

So when telling "ion" one should know whether in a solid, a plasma, or in a solvent and which one.

[clinz63]

Yeah. It is oversimplified. I made the assumption that the ions are always with their counterion because they usually are in undergraduate chem.

Yeah. Cl₂ would be reduced first.