those that form during chemical reactions without breaking down).

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Each time the half-life of a radioactive material occurs, the amount of the radioactive material decreases to half of the original value.

In order to calculate the half-life of a radioactive material, we use the following equation: For example, we can use the formula above to solve this problem: The radioisotope strontium-90 has a half-life of 38.1 years.

The rate of decay (given the symbol λ) is the fraction of the 'parent' atoms that decay in unit time.

For geological purposes, this is taken as one year.

Alpha decay is usually restricted to the heavier elements in the periodic table.

(Only a handful of nuclides with atomic numbers less than 83 emit an -particle.) The product of -decay is easy to predict if we assume that both mass and charge are conserved in nuclear reactions.

The time required for some materials to become stable may be minutes and, for others, thousands of years.

spontaneous decomposition of the nuclei of the atoms of radioactive substances.

The excess energy associated with this excited state is released when the nucleus emits a photon in the -ray portion of the electromagnetic spectrum.