why are some atomic
nuclei unstable?
 | Strong
nuclear force: a short-range, attractive force that acts among nucleons |
| Stable
nucleus: a nucleus that does not spontaneously decay to become the nucleus
of a different element |
| Unstable
nucleus: a nucleus that spontaneously undergoes decay to become the nucleus
of a different element |
| Transmutation:
a process by which a nucleus of one element is transformed into a nucleus of
a different element |
| Radioactivity:
the ability of unstable nuclei to undergo spontaneous nuclear decay. It is
also composed of alpha and beta/ |
| Binding
energy: the energy needed to separate nucleons within a nucleus or,
equivalently, the energy released by nucleons combining to form a nucleus.
Also calculated by applying Einstein’s equation, E=mc2 |
| Mass
defect: the difference between the mass of an atom and the sum of the masses
of its individual components |
| In
spite of repulsive forces their like charges, protons cluster tightly
together within the nucleus. The strong force in the nucleus overwhelms the
repulsive forces of the protons and holds protons and neutrons together |
| A
small percentage of atoms have nuclei that are unstable and subject to a
nuclear change called transmutation, which results in the formation of a new
element. Atoms that exhibit this behavior are called radioactive |
| This
stability of the nucleus is dependent on the neutron-proton ratio.
Stable atoms form a pattern called the band of stability |
what kinds of nuclear change occurs?
| Alpha
particle: a helium nucleus produced in nuclear decay |
| Beta
particle: an electron produced in nuclear decay |
| Gamma
ray: high-energy electromagnetic radiation produced by decaying nuclei |
| Radioactive
series: a sequence of nuclei that arise from and are transformed by
radioactive decay until a stable isotape is produced |
| Nuclear
fission: the process by which a nucleus splits into two smaller fragments |
| Chain
reaction: a self-sustaining nuclear or chemical reaction in which the
product from each step acts as the reactant for the next step |
| Critical
mass: the minimum mass of fissionable material needed to produce a chain
reaction |
| Nuclear fusion: the process by which two nuclei combine to form a heavier nucleus |
how is nuclear chemistry used?
| Half-life
is the time required for one half of the mass of a radioactive substance to
decay |
| The
half-life of the carbon- 14 isotype can be used to date organic material
that is up to 20,000 years old. Other radioactive isotypes are used to date
more ancient rock and mineral formations |
| The
effects of radiation may be measured in units called rems |