Lesson_5.3_Printable_PPT

Lesson_5.3_Printable_PPT - Nuclear Energy Since energy and...

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Since energy and mass are related by Einstein’s equation E = mc 2 , a discussion on mass of subatomic particles is necessary. Nuclear Energy The mass of atoms, molecules and atomic particles are measured in atomic mass unit (amu) By definition the unified atomic mass unit is equal to one- twelfth of the mass of the nucleus of a carbon-12 atom. Conceptually, it is 1 g divided by the Avogadro’s number and has an approximate value of 1.66 x 10 -27 kg Energy at subatomic level is measured in electron volt (eV) which is a measure of the kinetic energy acquired by an electron when accelerated by a potential difference of 1 volt. 1 electron volt = 1.60217646 × 10 -19 joules Masses of sub atomic particles are often measured in eV, meV, BeV and so on
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The mass of a proton is 1.0073 atomic mass unit (u) The mass of a neutron is 1.0087 u The mass of an electron is 0.0005486 u C-12 has a mass of 12 amu and its nucleus contains 6 protons and 6 neutrons The total mass of 6 protons and 6 neutrons is 12.096 How is this possible? When 12 particles having a total mass of 12.096 u joins together to form a nucleus, the mass is reduced to 12 u When a nucleus is formed by combining several particles, some mass is lost. This is called the mass defect and its equivalent energy is used in holding the nuclear particles together.
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The energy that holds the nuclear particles together is called binding energy. When nuclear particles escape the nucleus, part of the energy holding the nucleons together is released. This is the origin of γ radiations. If a massive nucleus splits into two pieces, the binding energy holding the pieces together is released. The total mass of the pieces is less than the mass of the original nucleus. The binding energy of the nucleus of any isotope can be calculated from the mass defect of the nucleus. This lost mass is called the mass defect and according to Einstein’s equation E = mc 2 , is the mass equivalent of the binding energy.
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The biding energy per nucleon is an important indicator of the stability of a nucleus, higher the binding energy per nucleon, the more stable it is. The greatest binding energy per nucleon occurs near mass number 56, then decreases for both more massive and less massive nuclei.
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Conversely less massive nuclei can combine together to gain stability, again with the release of energy. The slopes of the red line show these process, indicating that more energy is released when smaller nuclei fuse together than when massive nuclei split. More massive nuclei can gain stability by splitting into smaller nuclei releasing their binding energy.
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Nuclear Fission The process of splitting a massive nucleus into more stable less massive nuclei with the release of energy is called nuclear fission.
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Fission can occur when the nucleus of a heavy atom captures a neutron. In addition to energy, free neutrons are released during fission.
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Lesson_5.3_Printable_PPT - Nuclear Energy Since energy and...

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