Energy uranium nucleus

The equation shows that uranium-235 absorbs a neutron. After absorbing the neutron, the excited uranium nucleus splits and forms barium-141, krypton-92, and three neutrons. Energy is also produced in the reaction. This reaction is only one of a number of different ways that U-235 may split. Several hundred different isotopes have been identified when U-235 undergoes fission. 

The mass of each nucleon in a uranium nucleus is greater than the mass of each nucleon in any one of its fission fragments. This lost mass has been converted to energy, which is why nuclear fission is an energy-releasing process. 

If a uranium nucleus were to fission into three fragments of approximately equal size instead of two, would more energy or less energy be released Defend your answer using Figures 4.29 and 4.30. 

When the element uranium is bombarded by neutrons, a unique reaction called fission takes place. The uranium nucleus breaks into two pieces, which fly apart with a large release of energy. In addition, several extra neutrons are emitted. These cause more uranium nuclei to split apart, which creates more energy and more neutrons in a so-called chain reaction process. In an atomic bomb, the chain reaction becomes an uncontrolled explosion. In a nuclear power plant, the chain reaction is maintained in a steady state by control rods which absorb extra neutrons. 

D. decrease in binding energy per nucleon as the uranium nucleus breaks apart... 

But how could barium be formed from uranium No larger fragments than protons or helium nuclei (alpha particles) had ever been chipped away from nuclei, and the thought that a large number of them should be chipped off at once could be dismissed not enough energy was available to do that. Nor was it possible that the uranium nucleus could have been cleaved right across. Indeed a nucleus was not like a brittle solid that could be cleaved or broken Bohr had stressed that a nucleus was much more like a liquid drop. 

She remembered it in 1938, on the day before Christmas. She also had the packing fractions in her head, says Frisch—she had memorized Francis Aston s numbers for the mass defects of nuclei. If the large uranium nucleus split into two smaller nuclei, the smaller nuclei would weigh less in total than their common parent How much less That was a calculation she could easily work about one-fifth the mass of a proton less. Process one-fifth of the mass of a proton through E = mc. One fifth of a proton mass, Frisch exclaims, was just equivalent to 200 MeV. So here was the source for that energy it all fitted ... 

If a neutron penetrated a uranium nucleus, for example, the result might be fission. But if the neutron happened to be traveling at the appropriate energy when it penetrated—somewhere aroimd 25 eV—the nucleus would probably capture it without fissioning. Beta decay would follow, increasing the nuclear charge by one unit the result should be a new, as-yet-unnamed transuranic element of atomic number 93. That was one of Plac-zek s points. It would prove in time to be crucial. 

Most nuclei in nature are stable and remain intact indefinitely. Radionuclides, however, are unstable and spontaneously emit particles and electromagnetic radiation. Emission of radiation is one of the ways in which an unstable nucleus is transformed into a more stable one that has less energy. The emitted radiation is the carrier of the excess energy. Uranium-238, for example, is radioactive, undergoing a nuclear reaction emitting helium-4 nuclei. The helium-4 particles are known as alpha ( ) particles, and a stream of them is called alpha radiation. When a nucleus loses an alpha particle, the remaining fragment has an atomic number of 90 and a mass number of 234. The element with atomic number 90 is Th, thorium. Therefore, the products of uranium-238 decomposition are an alpha particle and a thorium-234 nucleus. We represent this reaction by the nuclear equation... 

This reaction is the lission of uranium nucleus by protons accelerated to very high energies. When such a fast proton hits uranium nucleus it produces something like an explosion with ejection of a multitude of particles, namely, six protons and 21 neutrons. Of course, the reaction is not due to a blind chance but is based on careful theoretical predictions. Uranium may be replaced with thorium. The reaction product, francium-212, for some time was considered to be the longest-lived isotope (a half-life of 23 min) but later the half-life was found to be only 19 min. 

To a certain extent, nuclei can be likened to drops of liquid and scientists have repeatedly tried to draw an analogy between the properties of a nucleus and those of a drop of liquid. If we transfer a sufficient energy to a drop and make it move it can break down to smaller drops. If a nucleus is excited (by a neutron, say) then it can also split into smaller fragments. Gradually, a uranium nucleus is deformed, it elongates, narrowing appears in it, and, finally, it splits into two parts. This is how Meitner and Frisch described the process of splitting of the uranium... 

Uranium fission caused by neutrons was forced or artificial. Not each uranium nucleus could be split and not each neutron could produce fission. When scientists had studied the fission mechanism in more detail they understood that the intensity of fission was higher under the effect of slow neutrons and if the uranium isotope with a mass number of 235 was used. The other uranium isotope, uranium-238, experienced fission only when bombarded by fast neutrons. Can there be a natural process similar to artificial uranium fission N. Bohr thought about that and put forward a hypothesis about possible spontaneous uranium fission (without external energy being transferred to the nuclei). 

In nuclear fission a heavy nuclide splits into two or more intermediate-sized fragments when struck in a particular way by a neutron. The fragments are called fission products. As the atom splits, it releases energy and two or three neutrons, each of which can cause another nuclear fission. The first instance of nuclear fission was reported in January 1939 by the German scientists Otto Hahn (1879-1968) and Fritz Strassmann (1902-1980). Detecting isotopes of barium, krypton, cerium, and lanthanum after bombarding uranium with neutrons led scientists to believe that the uranium nucleus had been split. 

Recall that nuclei of intermediate mass are the most stable. In nuclear fission, a very heavy nucleus splits into more-stable nuclei of intermediate mass. This process releases enormous amounts of energy. Nuclear fission may occur spontaneously or when nuclei are bombarded by particles. When uranium-235 is bombarded with slow neutrons, a uranium nucleus can capture one of the neutrons, making it very unstable. The nucleus splits into medium-mass nuclei with the emission of more neutrons. The mass of the products is less than the mass of the reactants. The missing mass is converted to energy. 

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