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In all of the above examples, the initial nuclide decays into just one product. [37] Consider the case of one initial nuclide that can decay into either of two products, that is A → B and A → C in parallel. For example, in a sample of potassium-40, 89.3% of the nuclei decay to calcium-40 and 10.7% to argon-40. We have for all time t:
A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example carbon-13 with 6 protons and 7 neutrons. The nuclide concept (referring to individual nuclear species) emphasizes nuclear properties over chemical properties, while the isotope concept (grouping all atoms of each element) emphasizes ...
In this definition, "stable" means a nuclide that has never been observed to decay against the natural background. Thus, these elements have half-lives too long to be measured by any means, direct or indirect. Stable isotopes: 1 element has 10 stable isotopes; 5 elements have 7 stable isotopes apiece; 7 elements have 6 stable isotopes apiece
A further 10 nuclides, platinum-190, samarium-147, lanthanum-138, rubidium-87, rhenium-187, lutetium-176, thorium-232, uranium-238, potassium-40, and uranium-235 have half-lives between 7.0 × 10 8 and 4.83 × 10 11 years, which means they have experienced at least 0.5% depletion since the formation of the Solar System about 4.6 × 10 9 years ...
An example is 64 29 Cu, which can decay either by positron emission to 64 28 Ni, or by electron emission to 64 30 Zn. Of the nine primordial odd–odd nuclides (five stable and four radioactive with long half lives), only 14 7 N is the most common isotope of a common element. This is the case because proton capture on 14 7 N
The center of the atom contains a tight ball of neutrons and protons, which is held together by the strong nuclear force, unless it is too large. Unstable nuclei may undergo alpha decay, in which they emit an energetic helium nucleus, or beta decay, in which they eject an electron (or positron). After one of these decays the resultant nucleus ...
An unintuitive consequence of this disequilibrium is that a sample of enriched material may occasionally increase in radioactivity as daughter products that are more highly radioactive than their parents accumulate. Both enriched and depleted uranium provide examples of this phenomenon.
Outside the nucleus, free neutrons are unstable and have a mean lifetime of 877.75 +0.50 −0.44 s [ 1 ] or 879.6 ± 0.8 s [ 2 ] (about 14 min and 37.75 s or 39.6 s , respectively). Therefore, the half-life for this process (which differs from the mean lifetime by a factor of ln (2) ≈ 0.693 ) is 611 ± 1 s (about 10 min , 11 s ).