radioactive decay

(noun)

Any of several processes by which unstable nuclei emit subatomic particles and/or ionizing radiation and disintegrate into one or more smaller nuclei.

Related Terms

  • nucleon

Examples of radioactive decay in the following topics:

  • Half-Life of Radioactive Decay

    • Radioactive decay is a random process at the single-atom level; is impossible to predict exactly when a particular atom will decay.
    • The following equation is used to predict the number of atoms (N) of a a given radioactive sample that remain after a given time (t):
    • This relationship between the half-life and the decay constant shows that highly radioactive substances are quickly spent, while those that radiate weakly endure longer.
    • A simulation of many identical atoms undergoing radioactive decay, starting with four atoms (left) and 400 atoms (right).
    • Nuclear half-life is the time that it takes for one half of a radioactive sample to decay.
  • Modes of Radioactive Decay

    • Radioactive decay occurs when an unstable atomic nucleus emits particles or light waves.
    • Radioactive decay occurs when an unstable atomic nucleus loses energy by emitting energy in the form of emitted particles or electromagnetic waves, called radiation.
    • 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.
    • In radioactive nuclei with too many neutrons, a neutron can be converted into an electron, called beta particle.
  • Indoor Pollution: Radon

    • Radon gas, the result of radium's radioactive decay, can severely compromise indoor air quality.
    • Radon is a dense, colorless, odorless noble gas that occurs naturally in the soil as the product of the radioactive decay of radium; it is a decay product of uranium and thorium, which occur naturally in the Earth's crust.
    • Radon decays to form daughters, or decay products, which include radioactive polonium, lead, and bismuth.
    • Radon is a gas, but these decay products are solids that can attach to dust and enter the lungs.
    • Radon and its daughters continue to decay in the lungs, releasing alpha and beta particles that can damage cellular DNA and result in lung cancer.
  • Rate of Radioactive Decay

    • Radioactive decay rate is exponential and is characterized by constants, such as half-life, as well the activity and number of particles.
    • 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.
  • Dating Using Radioactive Decay

    • Radiometric dating is used to date materials using the decay rate of a radioactive isotope.
    • In many cases, the daughter nuclide is radioactive, resulting in a decay chain.
    • The mathematical expression that relates radioactive decay to geologic time is:
    • Example of a radioactive decay chain from lead-212 (212Pb) to lead-208 (208Pb) .
    • The final decay product, lead-208 (208Pb), is stable and can no longer undergo spontaneous radioactive decay.
  • Balancing Nuclear Equations

    • In addition, problems will also often be given as word problems, so it is useful to know the various names of radioactively emitted particles.
    • Describes how to write the nuclear equations for alpha and beta decay.
  • Particle Accelerator

    • This occurs either through nuclear reactions in which an outside particle reacts with a nucleus, which can be supplied by a particle accelerator, or through radioactive decay, where no outside particle is needed.
    • Nuclear transmutation was first consciously applied to modern physics by Frederick Soddy when he, along with Ernest Rutherford, discovered that radioactive thorium was converting itself into radium in 1901.
    • Predicting the products of transmutation is like predicting the products of radioactive decay.
  • Nuclear Stability

    • However, if neutron count surpasses an ideal ratio, a nucleus becomes unstable and can undergo radioactive decay.
    • 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.
  • Transuranium Elements

    • Transuranium elements are those beyond uranium, none of which is stable because of radioactive decomposition.
    • None of these elements is stable and each of them decays radioactively into other elements.
    • They can also be created as common products of the decay of uranium and thorium.
    • Each of these elements is radioactive, with a half-life much shorter than the age of the Earth.
    • So, if any atoms of these elements were ever present at the Earth's formation, they have long since decayed.
  • Discovery of Radioactivity

    • The emission of these rays is called nuclear radioactivity, or simply radioactivity.
    • A nucleus that spontaneously destroys part of its mass to emit radiation is said to decay.
    • A substance or object that emits nuclear radiation is said to be radioactive.
    • Uranium is radioactive whether it is in the form of an element or compound.
    • Marie's radioactive fingerprints on some pages of her notebooks can still expose film.
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