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Electron Affinity and Energy
Name: Zunaira B.
Status: other
Age: 17
Location: N/A
Country: N/A
Date: 12/10/2002
Question:
I want to ask a question related to electron affinity.
Electron affinity is exothermic because energy is released when the
nucleus attracts an electron. My question is that why energy is released
when nucleus attracts an electron i.e why energy is released when
opposite charges attract each other?
Replies:
Zunaria,
Electron affinity is the energy change that occurs when an neutral atom in
the gaseous state acquires an electron to form a stable negative ion. As you
already know, electron affinities are exoenergetic. Exoenergetic processes
occur when the products of the process are lower in energy than the
reactants that formed them. Thus, large negative values associated with some
electron affinity values indicate that the ion formed is more stable than
the free atom and electron which formed it.
Regards,
ProfHoff 552
HOW the electron behaves, in this case the release of energy when the
nucleus attracts the electron, physics and chemistry describe remarkably
well. WHY and WHAT IS "REALLY" happening is far more complicated. Everything
that happens between electrons, protons, and photons (electromagnetic
radiation) is described, in principle, by a theory known as Quantum
ElectroDynamics, QED, developed by Richard Feynman, and others, 50 or so
years ago. The actual computations may require approximations, and be
exceedingly complicated, but the behavior is still understood "in
principle". QED says that electrons (and protons) by exchanging photons. How
well QED works is by comparison of the theoretical computation and
experimental measurement. QED predicts (a nasty calculation, but it has been
done) that the magnetic moment of the electron (a very fundamental property)
is: 1.00115965246 +/- 20 in the last two digits. The measured value is:
1.00115965221 +/- 4 in the last digit. That is about the width of a hair
compared to the distance from New York to Los Angeles! That is HOW electrons
behave. When you ask WHY? no one really knows. Physicists and chemists make
analogies between quantum behavior and classical objects (billiard balls and
the like) but we have no direct experience with that strange quantum world
and the analogies often fall apart if one tries to push them too hard. The
classical example of such failure is the problem of light emitted one photon
at a time and passing through two slits forming an interference pattern on a
detector screen on the other side of the barrier with the two slits (wave
behavior). But if you cover one of the slits, there is no interference
pattern (photon particle behavior). The paradox is, "How do photons leaving
the light source one at a time know whether one or the other or both slits
are open?" There is no question about HOW the photons behave, but we have no
macroscopic analogy to describe the mechanism of HOW IT HAPPENS (which just
a restatement of your question why the energy is released). Scientists have
grappled with the problem of classical analogies to quantum behavior, and
have not been successful in developing one that does not fail one way or
another. If you want to look further into the problems without having to
master the mathematics, I recommend the books: "QED" by Richard Feynman or
"Schrdinger's Cat" or "Schrdinger's Kittens" by John Gribbin. There are
others also. I know this response is long, but your question raises a lot of
very difficulties that almost become philosophical.
Vince Calder
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Update: February 2012
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