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### Topic: EGE Question  (Read 17780 times)

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#### abcc

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##### EGE Question
« on: February 12, 2007, 07:37:56 AM »
what is the difference between electron gain enthalpy & electron affinity??
why EGE is always negative
thx

#### chiralic

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##### Re: EGE Question
« Reply #1 on: February 12, 2007, 09:26:40 PM »
Electron Gain Enthalpy is the energy transfered when an electron is added to an atom, molecule or ion. It can be exothermic or endothermic. Also called Electron Affinity

Example:           A + e- ----> A-

deltaH = electron gain enthalpy and Electron Affinity = -(electron gain enthalpy)
• When deltaH is POSITIVE indicate A- is unstable relative to A
• When deltaH is NEGATIVE indicate A- is more stable than A

#### abcc

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##### Re: EGE Question
« Reply #2 on: February 13, 2007, 11:34:55 AM »
Electron Gain Enthalpy is the energy transfered when an electron is added to an atom, molecule or ion. It can be exothermic or endothermic. Also called Electron Affinity

Example:           A + e- ----> A-

deltaH = electron gain enthalpy and Electron Affinity = -(electron gain enthalpy)
• When deltaH is POSITIVE indicate A- is unstable relative to A
• When deltaH is NEGATIVE indicate A- is more stable than A

Actually, I still don't understand
As you said that EGE = EA
but why EA= - EGE

#### english

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##### Re: EGE Question
« Reply #3 on: February 13, 2007, 11:52:34 AM »
Usually, first EA is negative because you are adding an electron, of which feels a greater nuclear charge.  This releases energy.

Remember the Bohr model.  Going from n=2 to n=1 releases energy.  i.e., closer to the nucleus.

These are many-electron atoms, but I'm just using a simple example.

Second EA and higher EAs are positive.  Can you estimate why?
« Last Edit: February 13, 2007, 12:11:17 PM by k.V. »

#### abcc

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##### Re: EGE Question
« Reply #4 on: February 13, 2007, 12:13:57 PM »
Usually, first EA is negative becaue you are adding an electron, of which feels a greater nuclear charge.  This releases energy.

Remember the Bohr model.  Going from n=2 to n=1 releases energy.  i.e., closer to the nucleus.

These are many-electron atoms, but I'm just using a simple example.

Second EA and higher EAs are positive.  Can you estimate why?

ya
i know ~
EA is positive because energy is required to counterbalance the repulsion between the incoming  e- and the e- that in the atom
but..
so why EA= - electron gain enthalpy ?

#### english

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##### Re: EGE Question
« Reply #5 on: February 13, 2007, 12:17:04 PM »
EA, energy, it's all the same.  Your units are in enthalpy, my reference just indicates it as energy.  At constant pressure, E is H.

You're just stating EA in terms of energy released, which is negative.

#### maakii

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##### Re: EGE Question
« Reply #6 on: February 13, 2007, 12:25:39 PM »
I think he doesn't understand why

EGE is (-1 * EA) or the negative of EA

as written here: "Electron Affinity = -(electron gain enthalpy)"

#### abcc

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##### Re: EGE Question
« Reply #7 on: February 13, 2007, 12:37:55 PM »
I think he doesn't understand why

EGE is (-1 * EA) or the negative of EA

as written here: "Electron Affinity = -(electron gain enthalpy)"

BINGO
so , do you know why???

#### english

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##### Re: EGE Question
« Reply #8 on: February 13, 2007, 12:44:58 PM »
EGE is still negative, because the energy is flowing towards the surroundings of your system.

You can't say that -EA = -EGE => EA = EGE

Enthalpy and energy are the same thing in this case.

So to say that EA = -EGE is the same thing as saying EA = -E.

Where E is energy.

#### abcc

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##### Re: EGE Question
« Reply #9 on: February 13, 2007, 12:52:58 PM »
EGE is still negative, because the energy is flowing towards the surroundings of your system.

You can't say that -EA = -EGE => EA = EGE

Enthalpy and energy are the same thing in this case.

So to say that EA = -EGE is the same thing as saying EA = -E.

Where E is energy.

is it true that EGE is -ive?
My doctor told me that EA is +ive
so....EA =-EGE
but my question is if EA is the same thing as EGE, so why do they have different sign???
why EA is +ive, but EGE is -ive

#### english

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##### Re: EGE Question
« Reply #10 on: February 13, 2007, 12:55:09 PM »
I'm sorry I don't understand why EA would be positive in the physical sense.

#### abcc

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##### Re: EGE Question
« Reply #11 on: February 13, 2007, 12:58:17 PM »
I'm sorry I don't understand why EA would be positive in the physical sense.
EA is positive because energy is required to counterbalance the repulsion between the incoming  e- and the e- that in the atom

#### abcc

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##### Re: EGE Question
« Reply #12 on: February 13, 2007, 01:01:26 PM »
I'm sorry I don't understand why EA would be positive in the physical sense.
do you think that EA has the same meaning with EGE???
are they the same thing???
as i know, they both mean "adding electron" to atom
so , i think they are the same thing~
but if they are the same, why EA = -EGE, but not EA=EGE
I feel confused

#### maakii

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##### Re: EGE Question
« Reply #13 on: February 13, 2007, 01:49:38 PM »
according to wikipedia,

" It should be noted that the sign convention for electron affinity is the opposite to most thermodynamic quantities: a positive electron affinity indicates that energy is released on going from atom to anion."

Thus, EA is just another way of writing EGE. They are equal in all other respects other than EA is just -EGE -> opposite sign system.

#### abcc

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##### Re: EGE Question
« Reply #14 on: February 13, 2007, 01:57:46 PM »
according to wikipedia,

" It should be noted that the sign convention for electron affinity is the opposite to most thermodynamic quantities: a positive electron affinity indicates that energy is released on going from atom to anion."

Thus, EA is just another way of writing EGE. They are equal in all other respects other than EA is just -EGE -> opposite sign system.

regardness of the sign system?