WHat Exactly is Electron Affinity?

[bored]

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books say that electron affinity is the "change in energy when an electron is gained"
but I think some elements will release energy upon gaining and others will need energy to gain an electron.

So does that mean that the trend for electron affinity (same as ionization energy trend) only applies to non matels (because they release energy upon gaining)

ALso, can electron affinity be seen as the reduction potential? if the electron affinity is negative, that means negative energy change occurs meaning rxn is endothermic and so energy is released.

also, THis was a question that I was having trouble with.

Pb (s) + 2H+ (aq) --> 2Pb 2+ (aq) + H2 (g)

if this rxn is spontaneous, than which of the following has the highest electron affinity.

Pb (s)
H+ (aq)
Pb 2+ (aq)
H2 ( g)

 

[Temperature101]

books say that electron affinity is the "change in energy when an electron is gained"
but I think some elements will release energy upon gaining and others will need energy to gain an electron.

So does that mean that the trend for electron affinity (same as ionization energy trend) only applies to non matels (because they release energy upon gaining)

ALso, can electron affinity be seen as the reduction potential? if the electron affinity is negative, that means negative energy change occurs meaning rxn is endothermic and so energy is released.

also, THis was a question that I was having trouble with.

Pb (s) + 2H+ (aq) --> 2Pb 2+ (aq) + H2 (g)

if this rxn is spontaneous, than which of the following has the highest electron affinity.

Pb (s)
H+ (aq)
Pb 2+ (aq)
H2 ( g)

Is the answer H+? The way I define EA is the ability to pull or attract or gain electron from another atom...I look at it as a Redox reaction...When you gain electrons, your oxidation state decreases...H+ is the only element in the reactants that can gain electron to become H2 since the reaction is spontaneous. (not an equilibrium reaction). Dont know if my reasoning is correct......

 

[bored]

Well that is the answer, but I don't get how you came to that conclusion..

 

[Temperature101]

Well that is the answer, but I don't get how you came to that conclusion..

To make it simple...EA = Reduction Potential

 

[indianjatt]

Well that is the answer, but I don't get how you came to that conclusion..

Here is how I think of it. Which one of these reaction species wants an electron? Since EA is defined as the amount of energy released from the GAIN of an electron, an EA has to deal with gaining an electron. The degree of the EA is dependent on EN (up, right periodic trend). So in the case of your example, I would ask myself: Which chemical species gains an electron? H+ does in this case. The reaction is also favorable, which tells us that H+ gaining an electron is favorable and thus it should have a relatively large EA.

 

[Temperature101]

Here is how I think of it. Which one of these reaction species wants an electron? Since EA is defined as the amount of energy released from the GAIN of an electron, an EA has to deal with gaining an electron. The degree of the EA is dependent on EN (up, right periodic trend). So in the case of your example, I would ask myself: Which chemical species gains an electron? H+ does in this case. The reaction is also favorable, which tells us that H+ gaining an electron is favorable and thus it should have a relatively large EA.

Your reasoning is pretty much close to mine...I dont see any other way I can make clear for OP...However, if OP see EA = Reduction Potential, that in itself should make it simple.

 

[bored]

Thanks guys, that makes sense to me.