Examples of half-life in the following topics:
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- Given a sample of a particular radionuclide, the half-life is the time taken for half of its atoms to decay.
- The half-life is related to the decay constant.
- Half-lives vary widely; the half-life of 209Bi is 1019 years, while unstable nuclides can have half-lives that have been measured as short as 10−23 seconds.
- This means each half-life for element X is 18 days.
- Nuclear half-life is the time that it takes for one half of a radioactive sample to decay.
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- To find the half-life of the reaction, we would simply plug 5.00 s-1 in for k:
- To find the half-life, we once again plug in $\frac{[A]_0}{2}$for [A].
- Thus the half-life of a second-order reaction, unlike the half-life for a first-order reaction, does depend upon the initial concentration of A.
- Rearranging in terms of t, we can obtain an expression for the half-life:
- The half-life of a reaction is the amount of time it takes for it to become half its quantity.
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- After one half-life has elapsed, one half of the atoms of the nuclide in question will have decayed into a "daughter" nuclide, or decay product.
- Each step in such a chain is characterized by a distinct half-life.
- The half-life of Cs-137 is 30 years.
- First half-life (30 years): 100 grams of Cs-137 decays and 50 grams are left.
- Calculate the age of a radioactive sample based on the half-life of a radioactive constituent
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- 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.
- 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.
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- The half-life of a reaction describes the time needed for half of the reactant(s) to be depleted, which is the same as the half-life involved in nuclear decay, a first-order reaction.
- For a zero-order reaction, the half-life is given by:
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- Radioactive decay rate is exponential and is characterized by constants, such as half-life, as well the activity and number of particles.
- The half-life (t1/2) is the time taken for the activity of a given amount of a radioactive substance to decay to half of its initial value.
- Find the decay rate ($\lambda$) of element X, with a half-life of 2350 years.
- Since we are dealing with the half-life we will use values for N and No that are equivalent to 0.5.
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- The most stable radioisotope of hydrogen is tritium, with a half-life of 12.32 years.
- All heavier isotopes are synthetic and have a half-life less than a zeptosecond (10-21 sec).
- It has a half-life of 12.32 years.
- It decays through neutron emission with a half-life of 1.39 ×10−22 seconds.
- 6H decays through triple neutron emission and has a half-life of 2.90×10−22 seconds.
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- After approximately 5,730 years, half of the starting concentration of 14C will have been converted back to 14N.
- This is referred to as its half-life, or the time it takes for half of the original concentration of an isotope to decay back to its more stable form.
- Because the half-life of 14C is long, it is used to date formerly-living objects such as old bones or wood.
- Other elements have isotopes with different half lives.
- For example, 40K (potassium-40) has a half-life of 1.25 billion years, and 235U (uranium-235) has a half-life of about 700 million years.
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- Carbon compounds form the basis of all known life on Earth, and the carbon-nitrogen cycle provides some energy produced by the sun and other stars.
- Identification of carbon in NMR experiments is done with the isotope 13C. 14C is a radioactive isotope of carbon with a half-life of 5730 years.
- In total, there are 15 known isotopes of carbon and the shortest-lived of these is 8C, which decays through proton emission and alpha decay, and has a half-life of 1.98739 x 10−21 seconds.
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- It is an allotrope of oxygen that is much less stable than the diatomic allotrope (O2), breaking down with a half life of about half an hour in the lower atmosphere to O2.
- It is also unstable at high concentrations, decaying to ordinary diatomic oxygen (with a half-life of about half an hour in atmospheric conditions):