Radioactive isotopes alpha decay

Radioactive isotopes that decay by the emission of alpha or beta radiation undergo a change in the nature of their nuclei and are converted into isotopes of other elements. The emission of gamma rays, on the other hand, does not change the nature of the nuclei of the radioisotopes from which the rays are emitted. Gamma rays are a form of dissipation of nuclear energy. 

The nuclei of unstable atoms disintegrate or decay spontaneously, emitting alpha or beta particles and gamma radiation. Types of atoms that undergo this process are called radioactive isotopes. A decaying reactant isotope is referred to as a parent atom, and the atom produced is a daughter atom. In this ChemLab, heads-up pennies represent individual parent atoms of the fictitious element pennium, and tails-up pennies represent the daughter atoms of the decay. You will study the decay characteristics of pennium and will determine its half-life, which is the time required for one-half of the atoms to decay. 

Because exposure to radiation is a health risk, the administration of radioactive isotopes must be monitored and controlled carefully. Isotopes that emit alpha or beta particles are not used for Imaging, because these radiations cause substantial tissue damage. Specificity for a target organ is essential so that the amount of radioactive material can be kept as low as possible. In addition, an Isotope for medical Imaging must have a decay rate that is slow enough to allow time to make and administer the tracer compound, yet fast enough rid the body of radioactivity in as short a time as possible. 

While it is expected that the source rocks for the radionuclides of interest in many environments were deposited more than a million years ago and that the isotopes of uranium would be in a state of radioactive equilibrium, physical fractionation of " U from U during water-rock interaction results in disequilibrium conditions in the fluid phase. This is a result of (1) preferential leaching of " U from damaged sites of the crystal lattice upon alpha decay of U, (2) oxidation of insoluble tetravalent " U to soluble hexavalent " U during alpha decay, and (3) alpha recoil of " Th (and its daughter " U) into the solute phase. If initial ( " U/ U).4 in the waters can be reasonably estimated a priori, the following relationship can be used to establish the time T since deposition,... 

A particular isotope may undergo a series of nuclear decays until finally a stable isotope forms. For example, radioactive U-238 decays to stable Pb-206 in 14 steps, half of these are alpha emissions and the other half are beta emissions. 

In the second of their 1915 papers (Harkins and Wilson 1915b), Harkins and Wilson note from their study of the light elements (up to atomic number 27) that the main isotopic species had atomic masses which are integral multiples of 4. They concluded from this that, for those light nuclei, an important constituent must be the alpha particle just as it must be in the heavier radioactive nuclei which undergo alpha decay. In order to rationalize all the nuclei, including their nuclear charges, they... 

ISOTOPES All 41 isotopes of astatine are radioactive, with half-lives ranging from 125 nanoseconds to 8.1 hours. The isotope As-210, the most stable isotope with an 8.1-hour half-life, is used to determine the atomic weight of astatine. As-210 decays by alpha decay into bismuth-206 or by electron capture into polonium-210. 

ISOTOPES There are 37 isotopes of radon. All are radioactive. None are stable. They range in mass numbers from Rn-196 to Rn-228. Their half-lives range from a few microseconds to 3.8235 days for Rn-222, which is the most common. It is a gas that is the result of alpha decay of radium, thorium, or uranium ores and underground rocks. 

Uranium is the fourth metal in the actinide series. It looks much like other actinide metallic elements with a silvery luster. It is comparatively heavy, yet malleable and ductile. It reacts with air to form an oxide of uranium. It is one of the few naturally radioactive elements that is fissionable, meaning that as it absorbs more neutrons, it splits into a series of other lighter elements (lower atomic weights) through a process of alpha decay and beta emission that is known as the uranium decay series, as follows U-238—> Th-234—>Pa-234—>U-234—> Th-230 Ra-226 Rn-222 Po-218 Pb-2l4 At-218 Bi-2l4 Rn-218 Po-2l4 Ti-210—>Pb-210—>Bi-210 Ti-206—>Pb-206 (stable isotope of lead,... 

ISOTOPES There are a total of 23 isotopes of neptunium. None are stable. All are radioactive with half-lives ranging from two microseconds to 2.144xl0+ years for the isotope Np-237, which spontaneously fissions through alpha decay. 

The most important radioactive isotope of neptunium is Neptunium-237, with a half-life of 2.l44xl0+ years, or about 2.1 million years, and decays into protactinium-233 through alpha decay. Neptunium s most important use is in nuclear research and for instruments designed to detect neutrons. 

The most stable isotope of plutonium is Pu-244, with a half-life of S.OOxlO+ years (about 82,000,000 years). Being radioactive, Pu-244 can decay in two different ways. One way involves alpha decay, resulting in the formation of the isotope uranium-240, and the other is through spontaneous fission. 

ISOTOPES There are 24 isotopes of americium. All are radioactive with half-lives ranging from 72 microseconds to over 7,000 years. Five of americium s isotopes are fissionable with spontaneous alpha decay. 

ISOTOPES There are 23 isotopes of curium. All of them are man-made and radioactive. The most stable is curium-247, with a half-life of 1.56xl0+ years (156,600,000 years), which through alpha decay transmutates into plutonium-243. 

ISOTOPES There are a total of 21 isotopes of californium. None are found in nature and all are artificially produced and radioactive. Their half-lives range from 45 nanoseconds for californium-246 to 898 years for californium-251, which is its most stable isotope and which decays into curium-247 either though spontaneous fission or by alpha decay. 

ISOTOPES There are a total of 15 Isotopes for rutherfordlum, ranging from Rf-253 to Rf-264. Their half-lives range from 23 microseconds to 10 minutes. They are all artificially made, radioactive, and unstable. Their decay modes are a combination of alpha decay and spontaneous fission (SF). 

ORIGIN OF NAME Named after and in honor of the nuclear chemist Glenn T. Seaborg. ISOTOPES There a total of 16 Isotopes of unnilhexium (seaborgium) with half-lives ranging from 2.9 milliseconds to 22 seconds. All are artificially produced and radioactive, and they decay by spontaneous fission (SF) or alpha decay. 

Many radioisotopes exist, but not all radioisotopes are created equal. Radioisotopes break down through three separate decay processes (or decay modes) alpha decay, beta decay, and gamma decay. The following sections show you equations detailing each type of decay. Note The symbols showing the isotope notation for each radioactive isotope cire as follows or 2 Y, where... 

ACTINON. The name of the isotope of radon (emanation), which occurs in the naturally occurring actinium, series being, produced by alpha-decay of actinium X, which is itself a radium isotope. Achnon has an atomic number of 86, a mass number of 219, and a half-life of 3.92 seconds, emitting an alpha particle to form polonium-215 (Actinium A). See also Chemical Elements and Radioactivity. 

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... 

The isotopes ofHe do notalways occur in all natural samples in their usual proportion. Because helium has only two stable isotopes, variations in their abundance ratio are usually attributed to 3He. But in cases where radioactive alpha decays have enriched 4He, that reason for 4He richness is usually fairly obvious. One example is He in rocks containing uranium. The 4He/3He ratio is about 100 times greater than solar in the Earth s atmosphere because the history of radioactive decay of uranium in the Earth (Rutherford ) and its outgassing has enriched our atmosphere in daughter 4He. 

The naturally radioactive elements usually decay by emitting alpha particles their final decay product is usually a stable isotope of Pb there are four such "families" (often with branching) ... 

Radiation Hazard Natural isotope (Actinium-X, Actinium Series), Tl/2 = 11.4 days, decays to radioactive by alphas of... 

When an atom of any of these five isotopes decays, it emits an alpha particle (the nucleus of a helium atom) and transforms into a radioactive isotope of another element. The process continues through a series of radionuclides until reaching a stable, non-radioactive isotope of lead. The radionuclides in these transformation series (such as radium and radon), emit alpha, beta, and gamma radiations with energies and intensities that are unique to the individual radionuclide. 

One prominent and well-known kind of nuclear component is that which is produced by the decay of naturally occurring radionuclides (see Table 1). The best- and longest-known examples are He, produced by alpha decay of the natural isotopes of uranium and Th, and " Ar, produced in one branch of the beta decay of " K. (There are several other natural radionuclides which produce He by alpha decay, but whether because of low parent abundance and/or very slow decay, only in very unusual samples is the production of He not strongly dominated by uranium and thorium.) Since radioactive decay laws are well known, the ratio of daughter to parent isotope(s) in a closed system is a simple function of time, whence this phenomenon has been long and extensively exploited as a geochronometer (e.g., see Chapter 1.16). 

Both isotopes of He can also be radiogenic in origin. Most terrestrial and atmospheric He is radiogenic and has formed since the accretion of the Earth as a product of the alpha-decay of some naturally-occurring radioactive isotopes. On ejection from its parent isotope, an alpha particle (which is a He nucleus comprising two neutrons and two protons)... 

The alkali metals are not found free in nature, because they are so easily oxidized. They are most economically produced by electrolysis of their molten salts. Sodium (2.6% abundance by mass) and potassium (2.4% abundance) are very common in the earth s crust. The other lA metals are quite rare. Francium consists only of short-lived radioactive isotopes formed by alpha-particle emission from actinium (Section 26-4). Both potassium and cesium also have natural radioisotopes. Potassium-40 is important in the potassium-argon radioactive decay method of dating ancient objects (Section 26-12). The properties of the alkali metals vary regularly as the group is descended (Table 23-1). 

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