Standard 1e Preknowledge
1e) Students know some naturally occurring isotopes of elements are radioactive, as are isotopes formed in nuclear reactions.
CALIFORNIA FRAMEWORKS SUMMARY: Sometimes atoms with the same number of protons in the nucleus have different numbers of neutrons. These atoms are called isotopes of an element. Both naturally occurring and human-made isotopes of elements can be either stable or unstable. Less stable isotopes of one element, called parent isotopes, will undergo radioactive decay, transforming to more stable isotopes of another element, called daughter products, which can also be either stable or radioactive. For a radioactive isotope to be found in nature, it must either have a long half-life, such as potassium-40, uranium-238, uranium-235, or thorium-232, or be the daughter product, such as radon-222, of a parent with a long half-life, such as uranium-238.