Nuclear Review Sheet
Stability of an isotope is based on the ratio of neutrons and protons in its nucleus
Each radioactive isotope has a specific mode and rate of decay
A change in the nucleus of an atom that converts it from one element to another is called
transmutation. This can happen artificially or naturally
Half-life of a radioactive isotope is the time required for one-half of the nuclei of a given
sample of that isotope to disintegrate.
Half-life is not affected by any physical or chemical changes. Use table method to do half
life problems
Spontaneous decay can involve the release of alpha particles, beta particles, positrons,
and/or gamma radiation.
Alpha particles are the same as a Helium nucleus (2 protons and 2 neutrons)
Alpha particles have low penetrating power.
Alpha particles have a charge of +2 and will be attracted to a negative electrode
During alpha decay the mass will decrease by 4 and the atomic number will decrease by 2
Beta particles are the same as an electron and will be attracted to a positive electrode
Beta particles have a charge of –1 and a mass of 0
Beta particles have moderate penetrating power
During Beta decay the mass will stay the same and the atomic number will increase by 1
Gamma radiation has no charge and no mass
Gamma radiation has high penetrating power
Positrons are like positive electrons
Positrons have a charge of +1 and a mass of 0
During positron decay the mass will stay the same and the atomic number will decrease
by 1
Energy released in a nuclear reaction (fission or fusion) comes from a fractional amount
of mass that is converted to energy. This energy is much greater than a chemical reaction
When doing a nuclear equation the sum of the masses and atomic numbers on the left
must equal the sum of the masses and atomic numbers on the right
Fission reactions involve the splitting of heavier nuclei into lighter ones
Fission is brought about by the nucleus capturing slow moving neutrons
Only unstable elements of high atomic number can be fissioned. (ex. Uranium-235)
Radioactive wastes can be dangerous and stay radioactive for a very long time
Fusion occurs when two light nuclei fuse into a heavier nucleus at high temperature and
pressure.
The energy released is much greater than fission
The fuel is Hydrogen. The product is Helium
High energy is required because positive nuclei repel each other
Since radioisotopes are chemically similar to stable isotopes they can be used as tracers.
Radioisotopes are used in dating objects. Carbon 14 is used in biological substances and
Uranium-238 is used to date geological substances.
Isotopes with short half lives which will be quickly eliminated from the body are used to
diagnose diseases. Technetium 99 is used to pinpoint brain tumors. Iodine 131 is used to
diagnose thyroid disorders
Radium and Cobalt 60 are used in cancer therapy