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Chromium-51 is a synthetic radioactive isotope of chromium having a half-life of 27.7 days and decaying by electron capture with emission of gamma rays (0.32 MeV); it is used to label red blood cells for measurement of mass or volume, survival time, and sequestration studies, for the diagnosis of gastrointestinal bleeding, and to label platelets to study their survival.
The darker more stable isotope region departs from the line of protons (Z) = neutrons (N), as the element number Z becomes larger. This is a list of chemical elements by the stability of their isotopes. Of the first 82 elements in the periodic table, 80 have isotopes considered to be stable. [1] Overall, there are 251 known stable isotopes in ...
Conversely, of the 251 known stable nuclides, only five have both an odd number of protons and odd number of neutrons: hydrogen-2 , lithium-6, boron-10, nitrogen-14, and tantalum-180m. Also, only four naturally occurring, radioactive odd–odd nuclides have a half-life >10 9 years: potassium-40 , vanadium-50 , lanthanum-138 , and lutetium-176 .
Activation is inherently different than contamination. Neutrons are only free in quantity in the microseconds of a nuclear weapon's explosion, in an active nuclear reactor, or in a spallation neutron source. In an atomic weapon, neutrons are generated for only between 1 and 50 microseconds, but in huge numbers.
Isotope half-lives. The darker more stable isotope region departs from the line of protons (Z) = neutrons (N), as the element number Z becomes largerIsotopes are nuclides with the same number of protons but differing numbers of neutrons; that is, they have the same atomic number and are therefore the same chemical element.
The number of protons (Z column) and number of neutrons (N column). energy column The column labeled "energy" denotes the energy equivalent of the mass of a neutron minus the mass per nucleon of this nuclide (so all nuclides get a positive value) in MeV , formally: m n − m nuclide / A , where A = Z + N is the mass number.
This is a list of chemical elements and their atomic properties, ordered by atomic number (Z).. Since valence electrons are not clearly defined for the d-block and f-block elements, there not being a clear point at which further ionisation becomes unprofitable, a purely formal definition as number of electrons in the outermost shell has been used.
For example, uranium-238 usually decays by alpha decay, where the nucleus loses two neutrons and two protons in the form of an alpha particle. Thus the atomic number and the number of neutrons each decrease by 2 ( Z : 92 → 90, N : 146 → 144), so that the mass number decreases by 4 ( A = 238 → 234); the result is an atom of thorium-234 and ...