Radioactive nuclide Spontaneously

Radioactive decay usually involves one of three basic types of decay, a decay, (3 decay, or y decay in which an unstable nuclide spontaneously changes into a more stable form and emits some radiation. In Table 1.1, we summarize the basic features of these decay types. 

A radioactive nuclide (radioisotope) is spontaneously converted to another nuclide by one of the processes below each definition is followed by an example. As discussed above, all are accompanied with a loss of mass and a release of energy. 

Radioactivity the spontaneous adjustment of nuclei of unstable nuclides to a more stable state. 

Radioactive decay (radioactivity) the spontaneous decomposition of a nucleus to form a different nucleus. (21.1) Radiocarbon dating (carbon-14 dating) a method for dating ancient wood or cloth based on the rate of radioactive decay of the nuclide gC. (21.4)... 

Radioactive nuclides break down spontaneously in six principal ways, illustrated by the following examples ... 

The nuclide gCf emits neutrons through spontaneous fission in 3% of all decays, the rest being a-decays. All the other neutron sources listed involve a radioactive nuclide whose decay causes a nuclear reaction in a secondary substance which produces neutrons. For example, ffSb produces neutrons in beryllium powder or metal as a result of the initial emission of 7-rays, in which case there is no coulomb barrier to penetrate. Radium, polonium, plutonium, and americium produce neutrons by nuclear reactions induced in beryllium by the a-particles from their radioactive decay. For the neutrons produced either by spontaneous fission in californium or by the a-particle reaction with beryllium, the... 

U neutron, also known as deuterium), and (2 neutrons, also known as tritium). Anuclide is an elemental form distinguished from others by its atomic and mass numbers. Some nuclides, such as U and Cs, are radioactive and spontaneously decay to a different nuclide with the emission of characteristic energy particles or electromagnetic waves isomers of a given nuclide that differ in energy content are metastable (i.e., " Cd) and characterized in part, by the half-life of the isomer. 

The simplest, so-called ampoule, fission-based neutron sources contain either spontaneously fissioning nnclei or radioactive nuclides in homogeneous mixtures. The maximum neutron flnx of these sonrces is 10 n/s. 

Nuclear transformations generally possess very high activation barriers and are usually very slow, but even so, spontaneous changes of many heavy nuclides (e.g. and 9oTh) have been known since the nineteenth century. For the decay of a radioactive nuclide, Rutherford initially recognized three types of emission ... 

Some nuclides are unstable and spontaneously change into other nuclides, emitting energy in the form of radiation, either particulate (e.g. a and P particles) or electromagnetic (e.g. y-rays). This property is called radioactivity, and the nuclide showing it is said to be radioactive. Most nuclides occurring in nature are stable, but some are radioactive, for example, all the isotopes of uranium and thorium. Many other radioactive nuclides (or radionuclides) have been produced artificially, such as strontium-90, caesium-137 and the isotopes of the man-made elements, plutonium and americium. 

When considering all nuclides that occur in Nature, a distinction can be made between stable and radioactive nuclides (radionuclides). The nucleus of a radionuclide undergoes spontaneous radioactive decay, whereby it is converted into another nucleus. 

Since the radioactive half-lives of the known transuranium elements and their resistance to spontaneous fission decrease with increase in atomic number, the outlook for the synthesis of further elements might appear increasingly bleak. However, theoretical calculations of nuclear stabilities, based on the concept of closed nucleon shells (p. 13) suggest the existence of an island of stability around Z= 114 and N= 184. Attention has therefore been directed towards the synthesis of element 114 (a congenor of Pb in Group 14 and adjacent superheavy elements, by bombardment of heavy nuclides with a wide range of heavy ions, but so far without success. 

The discoveries of Becquerel, Curie, and Rutherford and Rutherford s later development of the nuclear model of the atom (Section B) showed that radioactivity is produced by nuclear decay, the partial breakup of a nucleus. The change in the composition of a nucleus is called a nuclear reaction. Recall from Section B that nuclei are composed of protons and neutrons that are collectively called nucleons a specific nucleus with a given atomic number and mass number is called a nuclide. Thus, H, 2H, and lhO are three different nuclides the first two being isotopes of the same element. Nuclei that change their structure spontaneously and emit radiation are called radioactive. Often the result is a different nuclide. 

Unstable nuclides decompose spontaneously Into other, more stable nuclides. These decompositions are called nuclear decay, and unstable nuclides are called radioactive. Three features characterize nuclear decays the... 

Decay, Radioactive—Transformation of the nucleus of an unstable nuclide by spontaneous emission of charged particles and/or photons (see Disintegration). 

Natural radioactivity derives from spontaneous nuclear disintegrations. Induced radioactivity derives from the bombardment of nuclei with accelerated subatomic particles or other nuclei. Both cause atoms of one nuclide to be converted to another nuclide. 

Radioactivity The process of spontaneous disintegration by a parent radionuclide, which releases one or more radiations and forms a daughter nuclide. When half the radioactivity remains, that time interval is designated the half-life (Tb 1/2). The Tb 1/2 value gives some insight into the behavior of a radionuclide and into its potential hazards. 

Scientists have known since 1896 that many nuclides are radioactive—that is, they spontaneously emit radiation. Early studies of radioactive nuclei, or radionuclides, by the New Zealand physicist Ernest Rutherford in 1897 showed that there are three common types of radiation with markedly different properties alpha (a), beta (f3), and gamma (y) radiation, named after the first three letters of the Greek alphabet. 

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