How protons remain sable in nucelus? They should repel protons and break the nucleus. how are they sable now??
Answers
Explanation:
The stability of neutrons within nuclei is explained by the energies which would be involved in the decay of a neutron which is spin paired with a proton. Although the correct explanation is not in terms of electrostatic force it is worthwhile to look at this force for a deuteron. A deuteron is a proton and neutron spinning about their center of mass. The proton and neutron are held together by the spin pairing force and the nuclear strong force. The potential energy of the deuteron is negative and it requires an input of energy to split a deuteron apart. But if the neutron of a deuteron decayed into a proton the deuteron would become a pair of protons a small distance apart. The potential energy of that arrangement can be easily computed. It is based upon the formula
V = ke²/s
where k is a constant, e is the charge of a proton and s is separation distance of the nucleon centers. Thus
V = 9×109(1.6×10-19)²/(2.25×10-15)
V = 1.024×10-13 joules
V = (1.024×10-13)(6.24×1018) electron volts
V = 6.4×105 eV
V = 0.64 MeV (million electron volts)
Thus in order to shift the nucleons of a deuteron into a proton spin pair would require the input of 0.64 MeV of energy. There is no place for this energy to come from so a neutron paired with a proton would be stable. However this is not the answer to the matter of the stability of neutrons within nuclei. The reason the above is not the answer to neutron stability is because the electron was left out of the computation. The creation of a proton-electron pair at that separation would create negative potential energy of −0.64 MeV. So the decay of a neutron is not prevented by the electrostatic force.
It is important to recognize that although neutron is electrically neutral it has a charge distribution. There is positive electrical charge in the interior of the neutron which is counter balanced by a negative charge toward the surface. The proton's charge distribution is all positive.
The binding energies of the three types of spin pairing are approximately equal the shift from a neutron-proton spin pairing to a proton-proton spin pairing would not prevent the decay of a neutron.
A possible alternative is the so-called nuclear strong force. According to the conventional theory of nuclear structure the interaction force between all combinations of neutrons and protons are attractions of the same magnitudes. Thus, according to the conventional theory, there is nothing to prevent the decay of a neutron within a nucleus.
There is an alternative to the conventional called the Alpha Module Model of nuclear structure. According that theory protons and neutrons have a strong force charge. If the strong force charge of a proton is designated as +1 then that of a neutron is −2/3. Thus unlike nucleons are attracted to each other and like one are repelled. A nucleus is held together by the spin pairing of the nucleons and the attraction of neutrons and protons for each other. Therefore if the neutron in a deuteron were to decay the potential energy due to the strong force would switch from one based upon an attraction proportional to 2/3 to one based upon a repulsion proportional to 1. This is not counter balanced by an effect on the electron produced by the decay. Electrons are not affected by the nuclear strong force. Without a source for this additional energy the neutron cannot decay. Hence the neutron in a deuteron is stable.
In a more complex nucleus such as an alpha particle the same would apply but with the additional complicating factor that the neutrons are spin paired with each other as well as with protons. Spin pairing is exclusive in the sense that a nucleon can form a spin pair with one and only one nucleon of the same type and one and only nucleon of the opposite type. Thus in an alpha particle if a neutron decays a violation of the exclusivity rule is created. Same applies in more complex nuclei because nucleons, wherever possible, are formed into modules of the form -n-p-p-n-, or equivalently -p-n-n-p-.
The decay of free neutrons is energy feasible because the mass of a neutron is greater than the sum of the masses of the proton and electron it decays into. But where a neutron is paired with a proton its decay is not energy feasible and thus such neutrons within nuclei are stable. This is according to the Alpha Module Model of nuclear structure. The conventional model of nuclear structure has nothing to say on this issue.
Answer:
Physicists have created one of the heaviest elements yet, an atom with 117 protons in its nucleus. This jumbo-sized atom sits on the outer reaches of the periodic table where bloated nuclei tend to become less and less stable. Element 117’s existence gives scientists hope, however, that they are getting closer to discovering a rumored “island of stability” where nuclei with so-called magic numbers of protons and neutrons become long-lived.
Elements heavier than uranium (with 92 protons) are not usually found in nature, but they can be forced into existence in laboratories. The trouble is: the larger an atomic nucleus gets, the more its protons repel one another with their positive charges, making it, in general, less stable, or more radioactive. Element 117, for example, has a half-life of about 50 thousandths of a second, meaning that within that time about half of it will decay into a lighter element.
A U.S.–Russian team first created element 117 in 2010 at the Joint Institute for Nuclear Research in Dubna, Russia. The element is still considered unofficial and has not yet been formally accepted and added to the periodic table by the International Union of Pure and Applied Chemistry (IUPAC). The new appearance of 117, in experiments by the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, Germany, should help the element gain official recognition. “In contrast to the first discovery, we are a different team at a different place using a different device,” says Christoph Dullmann, who led the GSI collaboration. “I think within the scientific community that will change the view on element 117 from an element that has been claimed to be observed to an element that is confirmed.”
To create 117, with the temporary periodic table placeholder name ununseptium, the researchers smashed calcium nuclei (with 20 protons apiece) into a target of berkelium (97 protons per atom). The experiment was so difficult in part because berkelium itself is tough to come by. “We had to team up with the only place on the planet where berkelium can be produced and isolated in significant quantities,” Dullmann says. That place is the Oak Ridge National Laboratory in Tennessee, which has a nuclear reactor that can create a rare element with a half-life of 330 days. It took the facility about two years to build up a large enough stock of berkelium for the experiment; when about 13 milligrams had accumulated, Oak Ridge scientists shipped it off to Germany for the next stage of the project. At GSI, researchers accelerated calcium ions to 10 percent light-speed and sent them colliding into the berkelium. If a calcium and berkelium nucleus collided head-on, occasionally the two nuclei would stick together, fusing to form a new element with a combined total of 117 protons. “We get about one atom per week,” Dullmann says.
The scientists did not observe element 117 directly. Instead, they searched for its daughter products after it radioactively decayed by emitting alpha particles—helium nuclei with two protons and two neutrons. “The heavy nuclei makes an alpha decay to produce element 115, and this also decays by alpha decay,” says Jadambaa Khuyagbaatar of GSI, lead author of a paper reporting the results published May 1 in Physical Review Letters.
After a few more steps in this decay chain, one of the nuclei produced is the isotope lawrencium 266—a nucleus with 103 protons and 163 neutrons that had never been seen before. Previously known isotopes of lawrencium have fewer neutrons and are less stable. This novel species, however, has an astonishingly long half-life of 11 hours, making it one of the longest-lived superheavy isotopes known to date. “Perhaps we are at the shore of the island of stability,” Dullmann says.
No one knows for sure where this island lies, or even if it exists at all. Theory suggests that the next magic numbers beyond those known are around 108, 110, or 114 protons, and 184 neutrons. These configurations, according to calculations, could lead to special properties that allow atoms to survive much longer than similar species. “All existing data for elements 116, 117 and 118 do confirm that lifetimes increase as one goes closer to the neutron number 184, says theorist Witold Nazarewicz of Oak Ridge, who was not involved in the study. “This is encouraging.”
Superheavy magic nuclei may turn out to have interesting shapes that confer stability, such as a so-called bubble configuration with a hole in the middle. “These have never been discovered yet, but the region that is being explored now is really on the edge of bubble territory,” Nazarewicz says.
Explanation:
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