Helium nuclei from radioactive decay

An alplia p uticle is an energetic helium nucleus. The alplia particle is released from a radioactive element witli a neutron to proton ratio tliat is too low. The helium nucleus consists of two protons and two neutrons. The alplia particle differs from a helimn atom in that it is emitted witliout any electrons. The resulting daughter product from tliis tj pe of transformation lias an atomic number Uiat is two less tluin its parent and an atomic mass number tliat is four less. Below is an e. aiiiple of alpha decay using polonium (Po) polonium has an atomic mass number of 210 (protons and neutrons) and atomic number of 84. 

The alpha particle is a helium nucleus produced from the radioactive decay of heavy metals and some nuclear reactions. Alpha decay often occurs among nuclei that have a favorable neutron/proton ratio, but contain too many nucleons for stability. The alpha particle is a massive particle consisting of an assembly of two protons and two neutrons and a resultant charge of +2. 

The alpha particle is a helium nucleus produced from the radioactive decay of heavy metals and some nuclear reactions. 

TRANSMUTATION. The natural or artificial transformation of atoms of one element into atoms of a different element as the result of a nuclear reaction. The reaction may be one in which two nuclei interact, as in the formation of oxygen from nitrogen and helium nuclei (/3-particles), or one in which a nucleus reacts widi an elementary particle such as a neutron or proton. Thus, a sodium atom and a proton form a magnesium atom. Radioactive decay, e.g., of uranium, can be regarded as a type of transmutation. The first transmutation was performed bv the English physicist Rutherford in 1919. 

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... 

Helium was identified by its characteristic emission spectrum as a component of the sun before it was found on earth. The major sources of helium on earth are natural gas deposits, where helium was formed from the a-particle decay of radioactive elements. The a particle is a helium nucleus that can... 

Radioactivity is characterized by the emission of energy (electromagnetic or in the form of a particle) from the nucleus of an atom, usually with associated elemental conversion. There are four basic types of radioactive decay (Table 5.4), of which alpha (a) and beta (p ) decay are most common in nature. Alpha emission is the only type of decay that causes a net mass change in the parent nuclide by loss of two protons plus two neutrons. Because two essentially weightless orbiting electrons are also lost when the equivalent of a helium nucleus is emitted, the parent nuclide transmutes into a daughter element two positions to the left on the periodic table. Thus decays by ot... 

The mode of radioactive decay is dependent upon the particular nuclide involved. We have seen in Ch. 1 that radioactive decay can be characterized by a-, jS-, and y-radiation. Alpha-decay is the emission of helium nuclei. Beta-decay is the creation and emission of either electrons or positrons, or the process of electron capture. Gamma-decay is the emission of electromagnetic radiation where the transition occurs between energy levels of the same nucleus. An additional mode of radioactive decay is that of internal conversion in which a nucleus loses its energy by interaction of the nuclear field with that of the orbital electrons, causing ionization of an electron instead of y-ray emission. A mode of radioactive decay which is observed only in the heaviest nuclei is that of spontaneous fission in which the nucleus dissociates spontaneously into two roughly equal parts. This fission is accompanied by the emission of electromagnetic radiation and of neutrons. In the last decade also some unusual decay modes have been observed for nuclides very far from the stability line, namely neutron emission and proton emission. A few very rare decay modes like C-emission have also been observed. 

Helium was identified by its characteristic emission spectrum as a component of the sun before it was found on earth. The major sources of helium on earth are natural gas deposits, where helium was formed from the a-particle decay of radioactive elements. The a particle is a helium nucleus that can easily pick up electrons from the environment to form a helium atom. Although helium forms no compounds, it is an important substance that is used as a coolant, as a pressurizing gas for rocket fuels, as a diluent in the gases used for deep-sea diving and spaceship atmospheres, and as the gas in lighter-than-air airships (blimps). 

Plutonium is formed and transmuted through radioactive decay. Three common types of radioactive processes involve the release of alpha or beta particles or gamma rays. Alpha decay results in the release of an alpha particle, which is a charged particle emitted from the nucleus of an atom having a mass and charge equal in magnitude to a helium nucleus (i.e., two protons and two neutrons). In alpha decay, the atomic mass of the nuclide is reduced by four and the atomic number by two. For example, plutonium-239 undergoes alpha decay to form uranium- 235. 

Radioactive nuclides contain atoms that disintegrate by emission of subatomic particles and gamma or X-ray photons. In alpha decay, a helium nucleus of 2 protons and 2 neutrons is emitted and reduces the mass number by 4 and the atomic number by 2. In beta decay, an electron - produced by the disintegration of a neutron into a proton, an electron, and an antineutrino - is emitted from the nucleus and increases the atomic number by 1 without changing the mass number. Sometimes a positron together with a neutrino is emitted. And sometimes an electron may be captured from the K (outermost) sheh of the atom the resultant electron hole in the K shell is filled by electrons from outer orbits and causes the emission of X-rays. Alpha and beta decay generally leave the resultant daughter nuclei in an... 

In light atoms, N/Z=l. The nuclide for instance, has six protons and six neutrons in its nucleus. The combination of a pair of protons with a pair of neutrons has particularly high stability. That group corresponds to the stable helium nucleus, which also remains after some radioactive decays and is emitted as alpha (a) particles. When radium disintegrates, a particles are emitted. Electrons from the environment are added to the helium nuclei and neutral helium atoms are formed. That is the reason why helium was discovered in uraninite. 

Atoms consist of comparatively large particles (protons and neutrons) that are concentrated in a central nucleus and smaller particles (electrons) that are relatively distant from the nucleus. If the number of protons in the nucleus equals the number of electrons in orbit, the atom is electrically neutral. If not, it is electrically charged and is known as an ion. Radioactivity is the result of the nucleus being unstable. An excess of neutrons results in the nucleus disintegrating by emitting electrons, also known as beta particles, in a process called beta decay. If the nucleus has an excess of protons, the nucleus can capture an electron, emit a positive electron (positron), or both. Another type of radioactivity, alpha decay, occurs in heavy elements when the nucleus emits a helium nucleus — two neutrons and two protons bound together. 

An alpha particle (a) is two protons and two neutrons bound together and is emitted from the nucleus during some kinds of radioactive decay. Alpha particles are helium nuclei and have a charge of 2+. They are often represented with the symbol He. Alpha emission is restricted almost entirely to very heavy nuclei. In these nuclei, both the number of neutrons and the number of protons need to be reduced in order to increase the stability of the nucleus. An example of alpha emission is the decay of 84Po into sfPb, shown in Figure 2.2. The atomic number decreases by two, and the mass number decreases by four. 

Radionuclides differ from other nuclei in that they emit ionizing radiation—alpha particles, beta particles, and gamma rays. The most massive of these emissions is the alpha particle, a helium nucleus of atomic mass 4, consisting of two neutrons and two protons. The symbol for an alpha particle is shown as the product of Reaction 4.10. An example of alpha production is found in the radioactive decay of uranium-238 ... 

Types of radiation Three principal types of radiation are given off during radioactive decay. One type is alpha radiation (a-radiation), which consists of alpha particles ejected from the nucleus. An alpha particle is equivalent to a helium-4 nucleus, that is, a nucleus with two protons and two neutrons. Alpha particles have a 2-1- charge. 

Nuclei which are radioactively unstable usually decay by the emission of one of three particles from the nucleus, traditionally labelled a, p and y particles. The largest, slowest and least penetrating of these are the a particles, which turn out to be the nucleus of the helium atom - i.e., two protons and two neutrons, with an overall charge of + 2. Decay by a emission is restricted to the heavier elements, and can be summarized in the following general equation ... 

In 1899 he identified two forms of radioactivity, which he called alpha and beta particles. As we saw earlier, he deduced that alpha particles are helium nuclei. Beta particles are electrons - but, strangely, they come from the atomic nucleus, which is supposed to be composed only of protons and neutrons. Before the discovery of the neutron this led Rutherford and others to believe that the nucleus contained some protons intimately bound to electrons, which neutralized their charge. This idea became redundant when Chadwick first detected the neutron in 1932 but in fact it contains a deeper truth, because beta-particle emission is caused by the transmutation ( decay ) of a neutron into a proton and an electron. 

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