Electron Potential Energy
Name: Joe B.
Date: 2001 - 2002
First a couple givens:
1. To find the energy on an electron in a specific atom in a certain
energy shell we use the equation E=(-k(Z^2))/(n^2)
2. We can use this to find the energy released when we move an electron
from the 1st shell to the 4th shell.
3. E is given in negative energy, as in the amount of energy that is lost
because the electron is in that shell captured by the atom. (and because
each shell can only hold so much energy so some must be lost for an
electron to enter that shell)
4. Einstin's (E=mc^2) says that as the speed increases so does the
mass. This means that the amount of energy increases without bound to
Now my question:
My Chemistry teacher says that a free atom (not one attached with an atom)
has an infinite amount of energy. How can this be? If the electron has an
infinite amount of energy and it take an infinite amount of energy to go
at or above the speed of light wouldn't the electron be able to go faster
than the speed of light or be able to power something else to go faster
than the speed of light? Doesn't this break Einstine's theory of relativity?
I don't agree that a free atom has infinite energy. Where did that come from???
It is conventional to choose as the "zero" of energy of an atomic state the
energy of the atom and an electron separated by a long distance (we say
infinite, but everyone agrees that the convention means large with respect to
the electron / nuclear distance. The only "absolute energy" that you can
assign to an atom (or any other particle(s) is its mass multiplied by c^2.
But because this number is so large compared to all the other energy
differences of interest in atomic and molecular computations and
measurements, other "zero" energies are mutually agreed upon, otherwise we
would always be taking the differences of to very large numbers, which is
Simple: a free electron does not have an infinite amount of energy. In
fact, a free electron at rest is considered to have zero energy. If it is
captured by a nucleus, its energy becomes negative, so some energy has to be
released to the surroundings.
Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois
This may be a case of misunderstanding ....
I think what your chemistry teacher means is that a free atom (not
one attached with an atom) has an infinite 'energy level', meaning that
'n', not 'E', in the equation below is infinite. This results in an
energy of 0. I.E., the state in which the electron is not bound to a
nucleus is the reference point for the energy measurements. For the
electron to bind to a nucleus and it must lose energy. Alternatively,
if you add energy to it, it is velocity must increase.
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Update: June 2012