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Radioactive decay, the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. Atomic energy is the source of nuclear power , which uses sustained nuclear fission to generate heat and electricity.
Like all nuclides with a high atomic number, these uranium nuclei require many neutrons to bolster their stability, so they have a large neutron-proton ratio (N/Z). The nuclei resulting from a fission ( fission products ) inherit a similar N / Z , but have atomic numbers that are approximately half that of uranium. [ 1 ]
Nuclei which have neutron numbers and proton numbers both equal to one of the magic numbers are called "doubly magic", and are generally very stable against decay. [13] The known doubly magic isotopes are helium-4, helium-10, oxygen-16, calcium-40, calcium-48, nickel-48, nickel-56, nickel-78, tin-100, tin-132, and lead-208.
A model of an atomic nucleus showing it as a compact bundle of protons (red) and neutrons (blue), the two types of nucleons.In this diagram, protons and neutrons look like little balls stuck together, but an actual nucleus (as understood by modern nuclear physics) cannot be explained like this, but only by using quantum mechanics.
Nuclei that exhibit an odd number of either protons or neutrons are less bound than nuclei with even number. A nucleus with full shells is exceptionally stable, as will be explained. As with electrons in the electron shell model, protons in the outermost shell are relatively loosely bound to the nucleus if there are only few protons in that ...
A chart or table of nuclides maps the nuclear, or radioactive, behavior of nuclides, as it distinguishes the isotopes of an element.It contrasts with a periodic table, which only maps their chemical behavior, since isotopes (nuclides that are variants of the same element) do not differ chemically to any significant degree, with the exception of hydrogen.
All "stable" isotopes (stable by observation, not theory) are the ground states of nuclei, except for tantalum-180m, which is a nuclear isomer or excited state. The ground state, tantalum-180, is radioactive with half-life 8 hours; in contrast, the decay of the nuclear isomer is extremely strongly forbidden by spin-parity selection rules.
This allowed the first estimates of the size of atomic nuclei. [2]: 255 Later experiments based on cyclotron acceleration of alpha particles striking heavier nuclei provided data for analysis of interaction between the alpha particle and the nuclear surface. However at energies that push the alpha particles deeper they are strongly absorbed by ...