radioactivity

(noun)

Spontaneous emission of ionizing radiation as a consequence of a nuclear reaction, or directly from the breakdown of an unstable nucleus.

Related Terms

  • decay

Examples of radioactivity in the following topics:

  • Discovery of Radioactivity

    • The emission of these rays is called nuclear radioactivity, or simply radioactivity.
    • 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.
    • Radium became highly desirable because it was about two million times as radioactive as uranium.
    • Marie's radioactive fingerprints on some pages of her notebooks can still expose film.
  • 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.
    • Each of these elements is radioactive, with a half-life much shorter than the age of the Earth.
    • Yellow - Radioactive elements: the most stable isotope has a half-life between 800 and 34.000 years.
    • Very little is known about these elements due to their extreme instability and radioactivity.
  • 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) .
    • Calculate the age of a radioactive sample based on the half-life of a radioactive constituent
  • 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.
  • 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.
    • The SI unit of radioactive activity is the becquerel (Bq), in honor of the scientist Henri Becquerel.
  • 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.
  • 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.
  • Measuring Radiation Exposure

    • It should not be confused with the unit of radioactive activity, the becquerel (Bq).
    • Exposure to a radioactive source will give a dose that is dependent on the activity, time of exposure, energy of the radiation emitted, distance from the source, and shielding.
    • People use these dosimeters to keep track of exposure, typically if they expect to come in contact with radioactive substances as part of their jobs.
  • The Alkaline Earth Metals

    • Most of the chemistry has been observed only for the first five members of the group; the chemistry of radium is not well established due to its radioactivity.
    • All isotopes of radium are radioactive.
    • The other non-radioactive members of the group are only present in smaller quantities.
    • Radium, with a maximum half-life of 1,601 years, is only present in nature when it is resupplied by a decay chain from the radioactive decay of heavier elements.
    • Radium has a low availability and is highly radioactive, making it toxic to life.
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