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Boron carbide's ability to absorb neutrons without forming long-lived radionuclides (especially when doped with extra boron-10) makes the material attractive as an absorbent for neutron radiation arising in nuclear power plants. [100] Nuclear applications of boron carbide include shielding, control rods and shut-down pellets.
Boron (5 B) naturally occurs as isotopes 10 B and 11 B, the latter of which makes up about 80% of natural boron. There are 13 radioisotopes that have been discovered, with mass numbers from 7 to 21, all with short half-lives, the longest being that of 8 B, with a half-life of only 771.9(9) ms and 12 B with a half-life of 20.20(2) ms.
An example of cosmic ray spallation is a neutron hitting a nitrogen-14 nucleus in the Earth's atmosphere, yielding a proton, an alpha particle, and a beryllium-10 nucleus, which eventually decays to boron-10. Alternatively, a proton can hit oxygen-16, yielding two protons, a neutron, and again an alpha particle and a beryllium-10 nucleus.
The only stable nuclides having an odd number of protons and an odd number of neutrons are hydrogen-2, lithium-6, boron-10, nitrogen-14 and (observationally) tantalum-180m. This is because the mass–energy of such atoms is usually higher than that of their neighbors on the same isobaric chain, so most of them are unstable to beta decay .
Neutrons stabilize the nucleus, because they attract protons, which helps offset the electrical repulsion between protons. As a result, as the number of protons increases, an increasing ratio of neutrons to protons is needed to form a stable nucleus; if too many or too few neutrons are present with regard to the optimum ratio, the nucleus ...
The other common isotope is 10 B at 19.78%, which contains 5 protons and 5 neutrons. [18] These are the only stable isotopes of boron; however other isotopes have been synthesised. Boron forms covalent bonds with other nonmetals and has oxidation states of 1, 2, 3 and 4. [19] [20] [21] Boron does not occur naturally as a free element, but in ...
This isotope makes up the vast majority of all naturally occurring indium despite its slight radioactivity. The shortest-lived is 7 B, with a half-life of a mere 350±50 × 10 −24 s, being the boron isotope with the fewest neutrons and a half-life long enough to measure. Some radioisotopes have important roles in scientific research; a few ...
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.