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Topic: Radioactive decay

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  Radioactive decay - Wikipedia, the free encyclopedia
Radioactive decay is the set of various processes by which unstable atomic nuclei emit subatomic particles (radiation).
Radioactive decay has been put to use in the technique of radioisotopic labelling, used to track the passage of a chemical substance through a complex system (such as a living organism).
On the premise that radioactive decay is truly random (rather than merely chaotic), it has been used in hardware random-number generators and is an invaluable tool in estimating the absolute ages of geological materials and young organic matter.
www.wikipedia.org /wiki/Radioactive_decay   (1973 words)

 NationMaster - Encyclopedia: Radioactive decay
The SI unit for measuring radioactive decay is the becquerel (Bq).
The radioactive half-life for a given radioisotope is a measure of the tendency of the nucleus to "decay" or "disintegrate" and as such is based purely upon that probability.
Radioactive decay is a statistical process which depends upon the instability of the particular radioisotope, but which for any given nucleus in a sample is completely unpredictable.
www.nationmaster.com /encyclopedia/Radioactive-decay   (532 words)

 radioactive decay - Hutchinson encyclopedia article about radioactive decay
In alpha decay (the loss of a helium nucleus – two protons and two neutrons) the atomic number decreases by two and a new nucleus is formed, for example, an atom of uranium isotope of mass 238, on emitting an alpha particle, becomes an atom of thorium, mass 234.
In beta decay the loss of an electron from an atom is accomplished by the transformation of a neutron into a proton, thus resulting in an increase in the atomic number of one.
For example, the decay of the carbon-14 isotope results in the formation of an atom of nitrogen (mass 14, atomic number 7) and the emission of a high-energy electron.
encyclopedia.farlex.com /radioactive+decay   (361 words)

 Radioactive decay   (Site not responding. Last check: 2007-09-20)
Radioactive decay is the process by which radionuclide s decay, emitting ionizing radiation.
The observed forms of decay are alpha decay, beta decay, electron capture, neutron emission, positron emission, proton emission, and spontaneous fission.
All radioactive decay is also associated with emission of gamma radiation in varying degrees.
www.serebella.com /encyclopedia/article-Radioactive_decay.html   (789 words)

 Radioactive Decay: .693   (Site not responding. Last check: 2007-09-20)
And, although radioactive decay is not a chemical process as such, it does follow first-order kinetics, and therefore the rates of radioactive decay are frequently expressed in terms of half-lives of radioactive isotopes.
Radioactive decay of the nuclei occurs at different rates, varying from a few millionths of a second, to even billions of years.
Thus, once more, the half-life of a radioactive isotope is represented by the time it takes one half of the sample of a particular isotope in question to undergo radioactive decay.
www.earthmatrix.com /radioactive/693.htm   (942 words)

 Radioactive decay rate depends on chemical environment
Radioactive dating is claimed to prove that the earth is billions of years old, but the methods are based on a number of unprovable assumptions.
Radioactive decay, being a nuclear process, is thus considered to be independent of external conditions.
Electron capture is the only radioactive decay mode that is recognised as possibly being affected by physical conditions such as pressure, but the effect is considered insignificant and is ignored.
www.answersingenesis.org /tj/v14/i1/decay_rate.asp   (1154 words)

 Radioactive decay and radioactivity
The third class of radioactive decay is gamma decay, in which the nucleus changes from a higher-level energy state to a lower level.
The activity of a sample of radioactive material (i.e., a bunch of unstable nuclei) is measured in disintegrations per second, the SI unit for this being the becquerel.
Radioactivity is often used in determining how old something is; this is known as radioactive dating.
buphy.bu.edu /~duffy/PY106/Radioactivity.html   (1644 words)

 Calculations with radioactivity
Since the decay of a large fraction of tritium atoms does not lead to a detectable number of photons, the efficiency of counting is much less than 100%.
The probability of decay at any particular interval is the same as the probability of decay during any other interval.
The decay of a population of radioactive atoms is random, and therefore subject to a sampling error.
www.curvefit.com /radioactivity_theory.htm   (1210 words)

 CF210: Constancy of Radioactive Decay Rates
The radioactive decay rates of nuclides used in radiometric dating have not been observed to vary since their rates were directly measurable, at least within limits of accuracy.
Present decay rates are likewise consistent with observations of the gamma rays and fading rates of supernova SN1991T, which is sixty million light-years away (Prantzos 1999), and with fading rate observations of supernovae billions of light-years away (Perlmutter et al.
Radioactive decay at a rate fast enough to permit a young earth would have produced enough heat to melt the earth (Meert 2002).
www.talkorigins.org /indexcc/CF/CF210.html   (490 words)

 Half Life and Radioactive Decay
An alpha particle (i.e., a helium nucleus) is released during alpha decay of a radioactive substance.
The rate of radioactive decay is related to the energy change that accompanies the transformation, but it is not a direct relationship.
The rate of decay of a radioactive nuclide is measured by its half-life.
library.thinkquest.org /27948/decay.html?tqskip1=1   (417 words)

 SurfWax: News, Reviews and Articles On Radioactive Decay
Decay is said to occur in the parent nucleus and produces a daughter.
Radioactive decay normally involves the emission of one of three types of particle: a helium nucleus consisting of two protons and two neutrons, an electron or a photon.
Radioactive decay as measured by Integral from Al 26 decay, and the signature of galactic rotation.
news.surfwax.com /physics/files/Radioactive_Decay.html   (4833 words)

 Physics 30: Atomic Physics - Half-Life and Radioactive Decay
Recognize that the decay constant is a measure of the rate of radioactive decay.
Recognize that the rate of decay of a radioactive nuclide is also measured and expressed by its half-life and its mean life.
Recognize that the expressed relationships for the radioactive decay are based on statistics and probability, and on the examination of the behaviour of a large number of individual situations.
www.sasked.gov.sk.ca /docs/physics/u8b3phy.html   (1434 words)

 Radioactive Decay
My question: is the rate of decay a constant no matter what the current atmospheric conditions are, in other words would the rate of decay be different on a different planet due to differences in gravity, atmosphere,temperature or whatever differences there are.
Since radioactive carbon is constantly being produced in the upper atmosphere by interaction of non-radioactive gases with sunlight, and we have no reason to believe that the rate of production has changed over earth's history, the assumption that the relative abundance in the atmosphere has not changed is is probably good.
Radioactive carbon dating has been checked against other methods, such as comparing the spacings in the growth rings of trees, where possible, and found to be correct.
www.newton.dep.anl.gov /askasci/phy99/phy99x43.htm   (790 words)

 Radioactive decay
Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles (radiation).
Radioactive decay results in a loss of mass, which is converted to energy (the disintegration energy) according to the formula
Of the commonly occurring forms of radioactive decay, the only one that changes the number of aggregate protons and neutrons (nucleons) contained in the nuclide is alpha emission, which reduces it by four.
www.omniknow.com /common/wiki.php?in=en&term=Radioactivity   (3547 words)

 Plate Rotation   (Site not responding. Last check: 2007-09-20)
Elements such as uranium, thorium, and plutonium are observed to emit particles and thereby undergo radioactive decay.
Radioactive decay is an exponential process such that half of the parent element will decay to the daughter element in a set amount of time (known as the half-life).
The primary elements in the decay series are shown with their relative abundances as individual bars, such that initially the parent element has an abundance of 1e10 atoms.
www.mines.utah.edu /~ggapps/radiation/radiation.html   (425 words)

 Law of radioactive decay   (Site not responding. Last check: 2007-09-20)
The law of radioactive decay predicts how the number of the not decayed nuclei of a given radioactive substance decreases in the course of time.
In this case a blue point for the time and the fraction of the not yet decayed nuclei is drawn into the diagram.
For example, even if the probability of a decay within the next second is 99 %, it is nevertheless possible (but improbable) that the nucleus decays after millions of years.
www.walter-fendt.de /ph14e/lawdecay.htm   (280 words)

 Radioactive Waste Management
The rate of decay of an isotope is inversely proportional to its half life; a short half life means that it decays rapidly.
Radioactive wastes occur at all stages of the nuclear fuel cycle, the process of producing electricity from nuclear materials.
For any of the radioactivity to reach human populations or the environment, all of these barriers would need to be breached before the radioactivity decayed.
www.uic.com.au /wast.htm   (3100 words)

 Teaching Radioactive Decay: Radioactive Half-Life and Dating Techniques
Students generate a radioactive decay table for an imaginary element (designed to simplify the math), use their data to plot a decay graph, develop the concept of half-life, and use the graph to "age" several samples.
During the students work and/or as a separate step after the graphs are completed, have the students explain what they have figured out about radioactive decay, half-life, isotopes, etc. from the exercise.
Determine the ratio of the radioactive atoms to the stable atoms.
www.accessexcellence.org /AE/AEPC/WWC/1995/teach_rad.html   (1324 words)

 SDV Nuclear Glossary   (Site not responding. Last check: 2007-09-20)
Radioactive disintegration by emission of an alpha particle.
Energy released by radioactive decay, through a nuclear reaction, or in the course of nuclear fission.
When applied to radioactive decay, the target nucleus is the parent nuclide, the daughter nucleus is the product nuclide, and there is no projectile.
glossary.dataenabled.com /sdvglossary_radioactive_decay.html   (1184 words)

 Theory: Radioactive Decay
It emerges from a weak decay process in which one of the neutrons inside an atom decays to produce a proton, the beta electron and an anti-electron-type neutrino.
It is produced as a step in a radioactive decay chain when a massive nucleus produced by fission relaxes from the excited state in which it first formed towards its lowest energy or ground-state configuration.
Alpha decay is also a type of fission, common because the alpha particle is a particularly low energy arrangement of two protons and two neutrons.
www2.slac.stanford.edu /vvc/theory/nuclearstability.html   (694 words)

 Radioactive Decay and Half-Life
Model the rate of decay of radioactive isotopes using a penny model.
Common isotopes to use are carbon-14, iodine-131, cobalt-60, hydrogen-3, strontium-90, and uranium-238, though any radioactive isotope with a known decay type and half-life can be used.
Previous instruction needs to be given in the types of radioactive decay and in the definition of half-life.
www.scienceteacherprogram.org /chemistry/stevens03.html   (478 words)

 Science NetLinks: Radioactive Decay: A Sweet Simulation of a Half-life
This predictability of decay rate allows radioactivity to be used for estimating the age of materials that contain radioactive substances....
To do this lesson and understand half-life and rates of radioactive decay, students should understand ratios and the multiplication of fractions, and be somewhat comfortable with probability.
In this lesson, students will be asked to simulate radioactive decay by pouring small candies, such as plain M&M'sĀ® or SkittlesĀ®, from a cup and counting which candies fall with their manufacturer's mark down or up.
www.sciencenetlinks.com /Lessons.cfm?DocID=178   (1190 words)

 A new mode of radioactive decay   (Site not responding. Last check: 2007-09-20)
This radioactive decay mode has been actively sought for 40 years by the nuclear physics community and opens a new avenue for the study of the atomic nucleus.
When this balance is upset by an excess of one or the other type of nucleons, the nucleus becomes unstable, which usually means that it disintegrates by beta emission, a process which transforms the extra neutron into a proton (emission of an electron, beta- radioactivity) or vice versa (emission of a positron, beta+ radioactivity).
The nuclear theory has predicted, since the 1960’s, that when this cohesive limit is reached for a very proton-rich nucleus it will emit either one or two protons (one-proton radioactivity and two-proton radioactivity), depending on whether it has, respectively, an odd or even number of protons to start with.
www.cnrs.fr /cw/en/pres/compress/radioactDecay.htm   (391 words)

 Exploratorium: Science Snacks: Radioactive Decay Model
In this model, the removal of a penny or a cube corresponds to the decay of a radioactive nucleus.
The smaller the chance of decay, the longer the half-life (time for half of the sample to decay) of the particular radioactive isotope.
For radon 217, the chance of decay is large: Its half-life is 1/1,000 of a second.
www.exploratorium.edu /snacks/radioactive_decay.html   (619 words)

 ONDRAF/NIRAS - Radioactive decay
Each time an atomic nucleus of a radioactive substance emits energy to attain better equilibrium between the number of protons and neutrons, another variant is created, which may or may not be radioactive.
This "dying down" of radioactivity is called radioactive decay.
The half-life of a radioactive material is the time it takes for the activity to reduce to half of its initial value.
www.nirond.be /engels/6.3.6_verval_eng.html   (200 words)

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