radioactivity

Examples of radioactivity in the following topics:

• Tracers

  • In a tracer, this substituting atom is a radioactive isotope.
  • This process is often called radioactive labeling.
  • Radioactive decay is much more energetic than chemical reactions.
  • There are two main ways in which radioactive tracers are used:
  • A radioactive compound can be introduced into a living organism.

• Radioactive Decay Series: Introduction

  • Radioactive decay series describe the decay of different discrete radioactive decay products as a chained series of transformations.
  • Radioactive decay series, or decay chains, describe the radioactive decay of different discrete radioactive decay products as a chained series of transformations.
  • The intermediate stages often emit more radioactivity than the original radioisotope.
  • For example, natural uranium is not significantly radioactive, but pitchblende, a uranium ore, is 13 times more radioactive because of the radium and other daughter isotopes it contains.
  • Not only are unstable radium isotopes significant radioactivity emitters, but as the next stage in the decay chain they also generate radon, a heavy, inert, naturally occurring radioactive gas.

• 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

• Biological Effects of Radiation

  • Although radiation was discovered in the late 19th century, the dangers of radioactivity and of radiation were not immediately recognized.
  • In the case of external exposure, the radioactive source is outside (and remains outside) the exposed organism.
  • Examples of external exposure include a nuclear worker whose hands have been dirtied with radioactive dust or a person who places a sealed radioactive source in his pocket.
  • In the case of internal exposure, the radioactive material enters the organism, and the radioactive atoms become incorporated into the organism.
  • When radioactive compounds enter the human body, the effects are different from those resulting from exposure to an external radiation source.

• 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.

• Models Using Differential Equations

  • A good example of a physical system modeled with differential equations is radioactive decay in physics.
  • Over time, radioactive elements decay.
  • The half-life, $t_{1/2}$, is the time taken for the activity of a given amount of a radioactive substance to decay to half of its initial value.
  • The mean lifetime, $\tau$ ("tau"), is the average lifetime of a radioactive particle before decay.
  • For a number of radioactive particles $N$, the activity $A$, or number of decays per time is given by:

• Natural Radioactivity

  • Detectable amounts of radioactive material occurs naturally in soil, rocks, water, air, and vegetation.
  • Radioactive material is found throughout nature.
  • The biggest source of natural background radiation is airborne radon, a radioactive gas that emanates from the ground.
  • Some of these decay products, like radium and radon, are intensely radioactive but occur in low concentrations.
  • Most of these sources have been decreasing, due to radioactive decay since the formation of the earth, because there is no significant source of replacement.