radioactive isotopes

(noun)

an atom with an unstable nucleus, characterized by excess energy available that undergoes radioactive decay and creates most commonly gamma rays, alpha or beta particles.

Related Terms

  • radiocarbon dating
  • half-life
  • isotope

Examples of radioactive isotopes in the following topics:

  • Dating Using Radioactive Decay

    • Radiometric dating is used to date materials using the decay rate of a radioactive isotope.
    • It is based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.
    • In many cases, the daughter nuclide is radioactive, resulting in a decay chain.
    • Here, t is age of the sample; D is number of atoms of the daughter isotope in the sample; D0 is number of atoms of the daughter isotope in the original composition; N is number of atoms of the parent isotope in the sample at time t (the present), given by N(t) = Noe-λt; and λ is the decay constant of the parent isotope, equal to the inverse of the radioactive half-life of the parent isotope times the natural logarithm of 2.
    • Calculate the age of a radioactive sample based on the half-life of a radioactive constituent
  • Study of Photosynthesis

    • Mass spectrometry has been used to study the ratio of carbon isotopes in various plants to understand the mechanisms of photosynthesis.
    • Mass spectrometry has been used to study the ratio of isotopes in various plants to understand the mechanisms of photosynthesis.
    • Stable carbon isotopes in carbon dioxide are utilized differentially by plants during photosynthesis.
    • Grasses in temperate environments, such as barley, rice, and wheat, follow a C3 photosynthetic pathway that yields distinctive isotopic ratios.
    • Describe the use of radioactive isotopes in the study of photosynthesis
  • Transuranium Elements

    • Green - Radioactive elements: the most stable isotope is very long-lived, with s half-life of over four million years.
    • Yellow - Radioactive elements: the most stable isotope has a half-life between 800 and 34.000 years.
    • Orange - Radioactive elements: the most stable isotope has a half-life between one day and 103 years.
    • Red - Highly radioactive elements: the most stable isotope has a half-life between several minutes and one day.
    • Purple - Extremely radioactive elements: the most stable isotope has a half-life less than several minutes.
  • Isotopes in Medicine

    • Nuclear medicine is a medical specialty that involves the application of radioactive substances to diagnose or treat disease.
    • Nuclear medicine is a medical specialty that involves the application of radioactive substances in the diagnosis and treatment of a disease.
    • Common isotopes that are used in nuclear imaging include: fluorine-18, gallium-67, krypton-81m, rubidium-82, nitrogen-13, technetium-99m, indium-111, iodine-123, xenon-133, and thallium-201.
    • For this type of therapy, yttrium-90 and iodine-131 are the most commonly used isotopes.
    • These images are scans used in the evaluation of thyroid cancer using the isotope iodine-123.
  • Isotopes

    • Isotopes do differ in their stability.
    • Neutrons, protons, and positrons can also be emitted and electrons can be captured to attain a more stable atomic configuration (lower level of potential energy) through a process called radioactive decay.
    • These atoms are called radioactive isotopes or radioisotopes.
    • Other elements have isotopes with different half lives.
    • Scientists often use these other radioactive elements to date objects that are older than 50,000 years (the limit of carbon dating).
  • Structural Determination

    • NMR analysis is isotope-dependent, and it often relies on trace isotopes of a molecule for detection.
    • Adding an isotope will also change the observed mass of any fragment which contains the isotope.
    • Isotopic labeling is used to track the passage of an isotope through a reaction, metabolic pathway, or cell.
    • In isotopic labeling, there are multiple ways to detect the presence of labeling isotopes: mass, vibrational mode, or radioactive decay.
    • The radioactive decay can be detected through an ionization chamber or autoradiographs of gels.
  • Modes of Radioactive Decay

    • Radioactive decay occurs when an unstable atomic nucleus emits particles or light waves.
    • Isotopes are atoms of the same element (thereby having the same number of protons) which differ in the number of neutrons in their nucleus.
    • Some isotopes of a given element are more unstable than others, causing a nuclear reaction which releases energy to achieve a more stable nuclear configuration.
    • Such isotopes are radioactive, and are referred to as "radioisotopes."
    • The higher the energy, the more the particles or light produced by radioactive decay will penetrate a substance.
  • Nuclear Stability

    • However, if neutron count surpasses an ideal ratio, a nucleus becomes unstable and can undergo radioactive decay.
    • Among elements of atomic number 1-82, only two (technetium and promethium) lack at least one isotope considered to be stable.
    • Only 90 isotopes in this region are believed to be perfectly stable, while 163 more are understood to be theoretically unstable but have never been observed to decay.
    • Technetium and promethium, as well as elements of number 83 and above, have only isotopes that will decay over time.
    • Stability of isotopes is shown as a function of proton and neutron numbers.
  • Isotopes of Hydrogen

    • Each isotope has different chemical properties.
    • It is radioactive, decaying into helium-3 through beta-decay accompanied by a release of 18.6 keV of energy.
    • It is a highly unstable isotope of hydrogen.
    • 5H is another highly unstable heavy isotope of hydrogen.
    • Unique among all stable isotopes, it has no neutrons.
  • Rate of Radioactive Decay

    • The decay rate of a radioactive substance is characterized by the following constant quantities:
    • The mean lifetime (τ, "tau") is the average lifetime of a radioactive particle before decay.
    • Total activity (A) is number of decays per unit time of a radioactive sample.
    • Radioactivity is one very frequent example of exponential decay.
    • Another unit of radioactivity is the curie, Ci, which was originally defined as the amount of radium emanation (radon-222) in equilibrium with one gram of pure radium, isotope Ra-226.
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