Nuclear
Chemistry
http://www.bcpl.net/~kdrews/nuclearchem/nuclear.html
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Following is a series of terms and
concepts that are related to the topic of Nuclear Chemistry.
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Alpha Emission:
Alpha particles are nuclear decay particles.
- They consist of two protons and two
neutrons.
- In essence, they are equivalent to a
helium nucleus.
- The particles are expelled from a
nucleus at a fairly low speed, approximately
one-tenth the speed of light.
- They are a minimal health risk to people
unless ingested or inhaled.
- The large mass nuclei tend to use alpha
emission because it is a quick way for a large mass
atom to lose a lot of nucleons.
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Beta Emission:
| Beta Emission is a nuclear decay
process. It is the process that ejects a high speed electron
from an unstable nucleus. The electron is formed on the spot
within the nucleus by the breakdown of a neutron into a
proton and electron. The electron is released from the
system. The proton that was formed remains behind in the
nucleus. As a result of the addition of the proton, the
atomic number of an element increases during beta emission.
Beta emission can be a significant health risk. |
Binding Energy:
| Binding Energy is the energy that
a nucleus releases in the process of trying to stabilize
itself. The nucleus converts some of its own mass into
energy. That energy is ejected from the nucleus. The process
of the loss of energy will then move the system further down
an energy level diagram. Thus, the system becomes more
stable. This process is necessary to relieve the instability
associated with having a large mass of positively charged
protons so close together. |
Binding Energy
Curve:
| The Binding Energy Curve helps to
understand the ideas behind fission and fusion. It is a
graph that plots the Binding Energy per Nucleon as a
vertical coordinate and the Mass Number of the elements as
the horizontal coordinate. |
| The graph peaks at a mass number
of 56. The more binding energy that is released per nucleon,
the more stable a nucleus is. Since 56 is the high point of
the graph, it means that any nucleus with a mass number of
56 will achieve the maximum stability possible. In theory,
all nuclei will try to become larger or smaller, as
necessary, so that they will eventually have a total of 56
nucleons in their structures. Elements to
the right of 56 would like to become smaller. They do so
with the process known as fission. Elements to the left of
56 would like to become larger. They do so with the process
known as fusion. |
Fission:
| Fission is the process known as
"splitting the atom." During fission, a large mass nucleus
is split into two or more smaller mass nuclei. Hopefully
during fission, the resulting new nuclei will have mass
numbers that are closer to 56. During the process large
quantities of energy are released as the products move up
the Binding Energy Curve. Fission is the currently used
process for the production of nuclear energy. |
Fusion:
| Fusion is the process that unites
small mass nuclei into a larger mass nucleus. During the
fusion process, the newly formed nucleus will have a mass
number that is closer to 56. During fusion extremely large
quantities of energy are released as the nuclei move up the
Binding Energy Curve. This is a much more efficient process
than fission. It produces considerably more energy that
fission. Unfortunately, it is very difficult to accomplish
and is not being utilized as a source of energy by society. |
Gamma Emission:
| Gamma Emission occurs primarily
after the emission of a decay particle. Gamma is a form of
high energy electromagnetic radiation. After a particle is
ejected from a nucleus the system may have some slight
excess of energy, or exist in a metastable state. This
slight excess of energy is released as gamma. Gamma emission
will not change the isotope or the element. The wavelength
of the emitted gamma radiation will be be unique to each
isotope. Gamma emission is a significant health risk. |
Mass Defect:
| Mass Defect is the mass in a
nucleus that is converted into energy. This energy is then
ejected from the nucleus to stabilize the system. The mass
defect will be the difference between the theoretical mass,
calculated as the sum of the parts of the nucleus, and the
experimental mass. This difference will be the mass that was
lost in the production of energy. |
Mass Number:
| Mass Number is the sum of the
nucleons in a given nucleus of the sum of the protons and
neutrons in a nucleus. |
Metastable Nucleus:
| A metastable nucleus is a nucleus
that has some slight excess of energy. The system has
probably ejected one or more particles during normal
radioactive decay. There is still a slight excess of energy
in the system. This is a metastable system. This slight
excess of energy is released as gamma radiation. |
Neutron-to-Proton
Ratio:
| Nuclei like to maintain a specific
ratio of neutrons-to-protons. If this ratio is not achieved,
then the system will experience some level of instability.
Generally, the first twenty elements prefer a ratio of
one-to-one. Elements beyond the first twenty will prefer
more neutrons than protons. Consequently, the ratio will be
a number that is greater than one. The preferred value for
that ratio is not well-defined. |
Nuclear Glue:
This is another name for Binding Energy.
Nucleons:
Nucleons are the primary
sub-atomic particles found in a nucleus. They are the
protons and neutrons.
- The sum of the nucleons in a nucleus is
called the
Mass Number.
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Isotopes of a specific
element will have the same number of protons, but
differing numbers of total nucleons.
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Nuclide:
| Nuclide is the general term for
any isotope of an element. As an example, an atom of
phosphorus with 15 protons and 15 neutrons is a specific
isotope of phosphorus. It could also be called a nuclide of
phosphorus. If an isotope had 15 protons and 16 neutrons, it
could also be referred to as a different nuclide of
phosphorus. When talking about a single nuclear species, the
term nuclide is often used. |
Radioactivity:
| Radioactivity is the spontaneous
decomposition of an unstable nucleus into a more stable
nucleus. It becomes a more stable nucleus by releasing
fragments or energy. Sometimes it releases both. In essence,
if a nucleus has some sort of a sturctural flaw then it is
unstable. That flaw may be the wrong combinations of protons
and neutrons. The flaw may be a problem with the level of
energy in the system. Whatever the flaw, if it is severe
enough, the nucleus will try to correct the problem. This
process of correcting the problem is known as radioactive
decay. |
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