Natural Radiation

Three types of natural radioactivity exist:

1. Isotopes with half-lives longer than one billion years, e.g.  ²³⁸U.
2. Daughter nuclides produced from the decay of these long-lived radioactive nuclides, e.g.  ²³⁴Th from alpha decay of ²³⁸U.
3. Nuclides that are still being produced as they decay, e.g.  ¹⁴C.

• The vast majority (80%) of stable nuclides have an even number of protons.
• Most elements with an odd number of protons have only a single stable isotope.
• Of the nuclides with an odd number of protons, nearly all (91%) have an even number of neutrons.
• Nuclides with 2, 8, 20, 28, 50, 82, or 126 protons or neutrons are unusually stable.

Radioactive nuclides with atomic numbers larger than 80 are grouped into four categories:

In the 4n series, all nuclides have atomic numbers that are multiples of 4.

In the 4n + 1 series, all nuclides have atomic numbers that are one number greater than multiples of 4.

In the 4n + 2 series, all nuclides have atomic numbers that are two numbers greater than multiples of 4.

In the 4n + 3 series, all nuclides have atomic numbers that are three numbers greater than multiples of 4.

Induced Radiation

First artificial radioactive isotope created by Irene Curie (daughter of Pierre and Marie) and Frederic Joliot in 1934. They bombarded aluminum metal with alpha particles in the following reaction: This reaction can also be written in the shorthand notation: Where the target nuclide is separated from the daughter nuclide by parentheses in which the particle that hits the target and the particle that is released are written.

• Induced radiation reactions have extremely large activation energies which can be overcome in linear accelerators or cyclotrons.
• Artificial radiation can is also produced inside nuclear reactors which contain thermal neutrons.

Next:  "Nuclear Fission"