Radioactivity types, alpha

Because of its radioactivity and alpha emission, polonium forms many types of radiolytic oxidation-reduction products. 

There are three main types of radioactive decay alpha particle emission, beta particle emission, and the emission of gamma radiation. When an unstable isotope undergoes radioactive decay, it produces one or more different isotopes. We represent radioactive decay using a nuclear equation. Two rules for balancing nuclear equations are given below. 

Table 32-1 lists the most important (from a chemist s viewpoint) types of radiation from radioactive decay. Four of these types — alpha particles, beta particles, gamma-ray photons, and X-ray photons —can be detected and recorded by the detector systems described in Section 12B-4. Most radittchcniical methods are based on counting the electronic signals produced when these decay particles or photons strike a radiation detector. 

I i) Panicles lost in radioactive dect are of two types alpha panicles (helium nuclei) and bm particles energy electrons). Identify p and R in the following equations. 

There are several types of radioactive decay alpha-particle production, in which an alpha particle (helium nucleus) is produced beta-particle (or electron) production the production of gamma rays (high-energy photons of light) and electron capture, in which one of the inner-orbital electrons is captured by the nucleus. Often a series of decays occurs before a radioactive nucleus attains a stable state. 

While Curie focused her work on discovering the different kinds of radioactive elements, Ernest Rutherford and others focused on characterizing the radioactivity itself. These scientists found that the emissions were produced by the nuclei of radioactive atoms. These nuclei were unstable and would emit small pieces of themselves in the form of electromagnetic radiation to gain stability. These were the particles that Becquerel and Curie detected. There are several different types of radioactive emissions alpha (a) rays, beta (/3) rays, gamma (y) rays, and positrons. 

The major types of natural radioactivity are alpha (a) decay, beta (jS) decay, gamma (7) ray emission, and positron emission. 

Gamma radiation is one of the three types of natural source of radioactivity. Gamma rays are electromagnetic radiation, like X-rays, and the other two types of natural radioactivity are alpha and beta radiation, which are in the form of particles. Gamma rays are the most energetic... 

Ernest Rutherford (1871-1937) identified two types of radiation from radioactive materials, alpha (a) and beta (j8). Alpha particles carry two fundamental units of positive charge and have essentially the same mass as helium atoms. In fact, alpha particles are identical to He ions. Beta particles are negatively charged particles produced by changes occurring within the nuclei of radioactive atoms and have the same properties as electrons. A third form of radiation, which is not affected by electric or magnetic fields, was discovered in 1900 by Paul Villard. This radiation, called gamma rays (y). 

The most important types of radioactive particles are alpha particles, beta particles, gamma rays, and X-rays. An alpha particle, which is symbolized as a, is equivalent to a helium nucleus, fHe. Thus, emission of an alpha particle results in a new isotope whose atomic number and atomic mass number are, respectively, 2 and 4 less than that for the unstable parent isotope. 

Gamma ray The shortest wavelength and highest energy type of all electromagnetic radiation. It originates in the nucleus of radioactive isotopes along with alpha particle, beta particle, or neutron emissions. 

There are three common ways by which nuclei can approach the region of stability (1) loss of alpha particles (a-decay) (2) loss of beta particles (/3-decay) (3) capture of an orbital electron. We have already encountered the first type of radioactivity, a-decay, in equation (/0). Emission of a helium nucleus, or alpha particle, is a common form of radioactivity among nuclei with charge greater than 82, since it provides a mechanism by which these nuclei can be converted to new nuclei of lower charge and mass which lie in the belt of stability. The actinides, in particular, are very likely to decay in this way. 

The origin of the rays was initially a mystery, because the existence of the atomic nucleus was unknown at the time. However, in 1898, Ernest Rutherford took the first step to discover their origin when he identified three different types of radioactivity by observing the effect of electric fields on radioactive emissions (Fig. 17.4). Rutherford called the three types a (alpha), (3 (beta), and y (gamma) radiation. 

The numerical combination of protons and neutrons in most nuclides is such that the nucleus is quantum mechanically stable and the atom is said to be stable, i.e., not radioactive however, if there are too few or too many neutrons, the nucleus is unstable and the atom is said to be radioactive. Unstable nuclides undergo radioactive transformation, a process in which a neutron or proton converts into the other and a beta particle is emitted, or else an alpha particle is emitted. Each type of decay is typically accompanied by the emission of gamma rays. These unstable atoms are called radionuclides their emissions are called ionizing radiation and the whole property is called radioactivity. Transformation or decay results in the formation of new nuclides some of which may themselves be radionuclides, while others are stable nuclides. This series of transformations is called the decay chain of the radionuclide. The first radionuclide in the chain is called the parent the subsequent products of the transformation are called progeny, daughters, or decay products. 

Radioactivity results when some part of an atom is unstable. The instability exists because the orbital electrons or the nucleus contain too much energy. Radioactive atoms are called radionuclides. They release excess energy by emitting radiation. The type of radiation released (alpha, beta, or gamma particles) may be more or less hazardous to humans, depending on the location of the radioactive materials. Exposure to radioactive materials outside the body poses external hazards. Radioactive materials may also be hazardous when ingested, inhaled, or injected and thus pose internal hazards. The sections below describe the characteristics of radiation particles as external or internal hazards and as they may be encountered after a terrorist attack. Chapter 3 provides additional details and addresses health effects associated with exposure to radiation. 

Most water systems are required to monitor for radioactivity and certain radionuclides, and to meet maximum contaminant levels (MCLs) for these contaminants, to comply with the Safe Drinking Water Act (SDWA). Currently, USEPA requires drinking water to meet MCLs for beta/photon emitters (includes gamma radiation), alpha particles, combined radium 226/228, and uranium. However, this monitoring is required only at entry points into the system. In addition, after the initial sampling requirements, only one sample is required every three to nine years, depending on the contaminant type and the initial concentrations. 

Ideally, measuring radioactivity in water assets in the field would involve minimal sampling and sample preparation. However, the physical properties of specific types of radiation combined with the physical properties of water make evaluating radioactivity in water assets in the field somewhat difficult. For example, alpha particles can only travel short distances and they cannot penetrate through most physical objects. Therefore, instruments designed to evaluate alpha emissions must... 

Radium is extremely radioactive. It glows in the dark with a faint bluish light. Radiums radioisotopes undergo a series of four decay processes each decay process ends with a stable isotope of lead. Radium-223 decays to Pb-207 radium-224 and radium-228decay to Pb-208 radium-226 decays to Pb-206 and radium-225 decays to Pb-209. During the decay processes three types of radiation—alpha (a), beta ((5), and gamma (y)—are emitted. 

Radioactivity of uranium can be measured by alpha counters. The metal is digested in nitric acid. Alpha activity is measured by a counting instrument, such as an alpha scintillation counter or gas-flow proportional counter. Uranium may be separated from the other radioactive substances by radiochemical methods. The metal or its compound(s) is first dissolved. Uranium is coprecipitated with ferric hydroxide. Precipitate is dissolved in an acid and the solution passed through an anion exchange column. Uranium is eluted with dilute hydrochloric acid. The solution is evaporated to near dryness. Uranium is converted to its nitrate and alpha activity is counted. Alternatively, uranium is separated and electrodeposited onto a stainless steel disk and alpha particles counted by alpha pulse height analysis using a silicon surface barrier detector, a semiconductor particle-type detector. 

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