Radioactive decay positron emission

There are other less common types of radioactive decay. Positron emission results in a decrease by one unit in the atomic number K capture involves the incorporation of one of the extranuclear electrons into the nucleus, the atomic number is again decreased by one unit. 

The remarkable feature of this transmutation was the fact that the nitrogen isotope produced was radioactive. These nitrogen atoms of mass 13 (rather than 14) underwent radioactive decay by emission of positive electrons, or positrons, to form stable carbon atoms of mass 13,... 

The various decay processes are listed in Table 1. Radioactive nuclides emit either nucleons (alpha particles, very rarely protons or neutrons) or electrons (negatrons, positrons). As an alternative to the emission of a positron, a proton may capture an electron of the K-shell (K-capture). By the emission of an alpha particle the mass number and the atomic number are reduced by the emission of electrons either the number of neutrons (jS -decay, negatron emission) or the number of protons ()S -decay, positron emission) is reduced. By K-capture also the number of protons is reduced. Due to the missing electron in the K-shell, characteristic X-rays of the newly produced atomic species are emitted. 

The great majority of nuclei are unstable and undergo various types of radioactive decay a decay, p decay, positron emission, electron capture, and -y emission. In nuclear reactions, total mass number (A) and total charge (Z) must be balanced. A plot of number of neutrons (N) versus number of protons (Z) for all nuclei shows a narrow band of stable nuclei. To become more stable the type of decay can often be predicted from the N/Z ratio of the unstable nucleus. Certain heavy nuclei undergo a series of decays to reach stabiity. 

A much rarer form of radioactivity is positron emission, where a proton in the nucleus changes into a neutron, the unit of positive charge being removed by the emission of a positron, a particle with the same mass as the electron, but with a charge of opposite sign. An example is the decay of cobalt-56 to iron-56 ... 

The product, phosphorus-30, is radioactive, decaying by positron emission ... 

Effects of different modes of radioactive decay on the position of an isotope on the Chart of the Nuclides. Beta-decay, which changes a neutron to a proton, moves the nuclide up and to the left. Positron decay or electron capture, which changes a proton into a neutron, moves the nuclide down and to the right. And -decay, which is the emission of a 4He nucleus, moves the nuclide down and to the left. 

The term antineutrino usually denotes an antiparticle whose emission is postulated to accompany radioactive decay by negatron emission, such as, for example, in neutron decay into a proton p+, negatron e and aiiliiieulnno IT, expressed by the equatiuii n p+ + e + vj. Capture of a neutrino by the neutron, ve + n - p+ + e would be an equally good description of the process. Positron emission is accompanied by a neutrino,... 

Another trend is that radioactive nuclei with higher neutron/proton ratios (top side of the band) tend to emit j8 particles, while nuclei with lower neutron/proton ratios (bottom side of the band) tend to undergo nuclear decay by positron emission, electron capture, or a emission. This makes sense if you think about it The nuclei on the top side of the band are neutron-rich and therefore undergo a process that decreases the neutron/proton ratio. The nuclei on the bottom side of the band, by contrast, are neutron-poor and therefore undergo processes that increase the neutron /proton ratio. (Take a minute to convince yourself that a emission does, in fact, increase the neutron/proton ratio for heavy nuclei in which n > p.)... 

Radioactivity is the spontaneous emission of radiation from an unstable nucleus. Alpha (a) radiation consists of helium nuclei, small particles containing two protons and two neutrons (fHe). Beta (p) radiation consists of electrons ( e), and gamma (y) radiation consists of high-energy photons that have no mass. Positron emission is the conversion of a proton in the nucleus into a neutron plus an ejected positron, e or /3+, a particle that has the same mass as an electron but an opposite charge. Electron capture is the capture of an inner-shell electron by a proton in the nucleus. The process is accompanied by the emission of y rays and results in the conversion of a proton in the nucleus into a neutron. Every element in the periodic table has at least one radioactive isotope, or radioisotope. Radioactive decay is characterized kinetically by a first-order decay constant and by a half-life, h/2, the time required for the... 

Electron emission (ft -) A type of radioactive decay, where a neutron in the nucleus of an unstable atom converts into a proton and releases an electron and an antineutrino (compare with electron capture and positron emission). 

Positron emission (fi+) A type of radioactive decay where a proton converts into a neutron, positron, and neutrino (compare with electron emission). 

In some radioactive decays, one proton is transformed into one neutron and a positively charged particle with the same mass as a beta 0") particle (or electron) is produced. Emission of this positively charged particle is known as positron emission. Positrons (antielectrons) are symbolized as P+ or e. The nuclear equation of the formation of a positron particle is i . i . o ... 

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