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Electron Capture (EC, K-capture)
| Nuclei having an 1)…………. of protons may capture an electron from one of the inner orbits which 2)……………… combines with a proton in the nucleus to form a neutron. This process is called electron capture (EC). The electron is normally captured from the innermost orbit (the K-shell), and, 3)……………, this process is sometimes called K-capture. A neutrino is formed at the same time that the neutron is formed, and energy carried off by it serves to 4)………… momentum. Any energy that is available due to the atomic mass of the product being appreciably less than that of the parent will appear as gamma 5)………. Also, there will always be characteristic x-rays given off when an electron from one of the higher energy shells moves in to fill the 6)……….. in the K-shell. Electron capture and positron 7)……….. result in the production of the same daughter product, and they exist as competing processes. For positron emission to occur, however, the mass of the daughter product must be less than the mass of the parent by an amount equal to at least twice the mass of an electron. This mass 8)…………… between the parent and daughter is necessary to account for two items present in the parent but not in the daughter. One item is the positron ejected from the nucleus of the parent. The other item is that the daughter product has one less 9)………… election than the parent. If this 10)………… is not met, then orbital electron capture takes place exclusively. | 2. EXCESSIVE 3. IMMEDIATE 4. CONSEQUENCE 5. CONSERVATION 6. RADIATE 7. VACANT 8. EMIT 9. DIFFERENT 10. ORBIT 11. REQUIRE |
3.4. Translate the sentences summarizing the topic on the modes of radioactive decay:
1. Alpha decay is the emission of an alpha particle (2 protons and 2 neutrons) from an unstable nucleus. The daughter nuclide has an atomic number 2 less than the parent nuclide and a mass number 4 less than the parent nuclide. The daughter nucleus commonly releases its excitation energy by gamma emission.
2. Beta-minus decay effectively converts a neutron to a proton and an electron, which is immediately ejected from the nucleus. The daughter nuclide has its atomic number increased by 1 and the same mass number compared to the parent.
3. Beta-plus decay effectively converts a proton to a neutron and a positron, which is immediately ejected from the nucleus. The daughter nuclide has its atomic number decreased by 1 and the same mass number compared to the parent.
4. In electron capture, the nucleus absorbs an electron from the innermost orbit-This electron combines with a proton to form a neutron.
5. Internal conversion occurs when a gamma ray, emitted by the nucleus as it goes from the excited state to the ground state, interacts with one of the innermost electrons of the same atom. The electron is ejected from the atom.
6. An isomeric transition is the decay of an excited nucleus to a lower-energy level by the emission of a gamma ray.
7. Decay chains can be found by tracing the steps an unstable atom goes through as it tries to achieve stability.
8. Many modes of radioactive decay result in a daughter nuclide that has an energy level above the ground state. This excitation energy is usually released immediately in the form of a gamma ray.
9. The type of decay that a nuclide will typically undergo can be determined by its relationship to the line of stability on the Chart of the Nuclides. Nuclides that lie below and to the right of the line of stability will typically beta minus decay. Nuclides above and to the left of the line will typically beta plus decay or electron capture. Most alpha emitters are found in the upper, right-hand corner of the chart.
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