Isotopes, unstable

Natural neon is a mixture of three isotopes. Six other unstable isotopes are known. 

Naturally occurring zinc contains five stable isotopes. Sixteen other unstable isotopes are recognized. 

Natural vanadium is a mixture of two isotopes, 50V (0.24%) and 51V (99.76%). 50V is slightly radioactive, having a half-life of > 3.9 x 10i7 years. Nine other unstable isotopes are recognized. 

Natural yttrium contains but one isotope, 89Y. Nineteen other unstable isotopes have been characterized. 

Naturally occurring krypton contains six stable isotopes. Seventeen other unstable isotopes are now recognized. The spectral lines of krypton are easily produced and some are very sharp. While krypton is generally thought of as a rare gas that normally does not combine with other elements to form compounds, it now appears that the existence of some krypton compounds is established. Krypton difluoride has been prepared in gram quantities and can be made by several methods. A higher fluoride of krypton and a salt of an oxyacid of krypton also have been... 

Ordinary tin is composed of nine stable isotopes 18 unstable isotopes are also known. Ordinary tin is a silver-white metal, is malleable, somewhat ductile, and has a highly crystalline structure. Due to the breaking of these crystals, a "tin cry" is heard when a bar is bent. 

Atoms with the same number of protons but a different number of neutrons are called isotopes. To identify an isotope we use the symbol E, where E is the element s atomic symbol, Z is the element s atomic number (which is the number of protons), and A is the element s atomic mass number (which is the sum of the number of protons and neutrons). Although isotopes of a given element have the same chemical properties, their nuclear properties are different. The most important difference between isotopes is their stability. The nuclear configuration of a stable isotope remains constant with time. Unstable isotopes, however, spontaneously disintegrate, emitting radioactive particles as they transform into a more stable form. 

Radon daughters The series of unstable isotopes that are formed as radon atoms undergo radioactive decay. 

Unstable isotopes decompose (decay) by a process referred to as radioactivity. Ordinarily the result is the transmutation of elements the atomic number of the product nucleus differs from that of the reactant. For example, radioactive decay of produces a stable isotope of nitrogen, N. The radiation given off (Figure 2.6) may be in the form of—... 

Because the path of the s process is blocked by isotopes that undergo rapid beta decay, it cannot produce neutron-rich isotopes or elements beyond Bi, the heaviest stable element. These elements can be created by the r process, which is believed to occur in cataclysmic stellar explosions such as supemovae. In the r process the neutron flux is so high that the interaction hme between nuclei and neutrons is shorter that the beta decay lifetime of the isotopes of interest. The s process chain stops at the first unstable isotope of an element because there is time for the isotope to decay, forming a new element. In the r process, the reaction rate with neutrons is shorter than beta decay times and very neutron-rich and highly unstable isotopes are created that ultimately beta decay to form stable elements. The paths of the r process are shown in Fig. 2-3. The r process can produce neutron-rich isotopes such as Xe and Xe that cannot be reached in the s process chain (Fig. 2-3). 

Some isotopes that occur in nature are unstable and are said to be radioactive. A few radioactive isotopes, such as uranium-238 and carbon-14, are found on Earth, and many others can be synthesized in nuclear chemistry laboratories, as we describe in Chapter 22. Over time, radioactive isotopes decompose into other stable isotopes. Unstable isotopes decompose in several ways. Most nuclei that have Z > 83 decompose by giving off a helium... 

Each different unstable isotope has its own characteristic rate of decomposition. Some isotopes survive for only a fraction of a second, but others decompose slowly, sometimes over thousands of years. Most of chemistry involves the stable isotopes, so we defer further consideration of nuclear decomposition until Chapter 22, which covers nuclear processes In detail. 

The isotopic molar masses of all stable and many unstable isotopes have been determined using mass spectrometry, as described in Section 2-. These masses can be found in standard data tables. We provide values as needed for calculations. Example illustrates the calculation of nuclear binding energies from isotopic molar... 

Explain how the unstable isotope O can be used to show whether the oxygen atom in the water molecule comes from the carboxylic acid or from the alcohol. 

In addition to these two common radioactive emissions, some isotopes emit neutrons when they decay. This usually happens with highly unstable isotopes. The degree of instability is measured by the isotope s half-life, which is the time it takes for... 

The planets nearest the Sun have a high-temperature surface while those further away have a low temperature. The temperature depends on the closeness to the Sun, but it also depends on the chemical composition and zone structures of the individual planets and their sizes. In this respect Earth is a somewhat peculiar planet, we do not know whether it is unique or not in that its core has remained very hot, mainly due to gravitic compression and radioactive decay of some unstable isotopes, and loss of core heat has been restricted by a poorly conducting mainly oxide mantle. This heat still contributes very considerably to the overall temperature of the Earth s surface. The hot core, some of it solid, is composed of metals, mainly iron, while the mantle is largely of molten oxidic rocks until the thin surface of solid rocks of many different compositions, such as silicates, sulfides and carbonates, occurs. This is usually called the crust, below the oceans, and forms the continents of today. Water and the atmosphere are reached in further outward succession. We shall describe the relevant chemistry in more detail later here, we are concerned first with the temperature gradient from the interior to the surface (Figure 1.2). The Earth s surface, i.e. the crust, the sea and the atmosphere, is of... 

Radioactive decay is a nuclear process from an intrinsically unstable nucleus that emits alpha particles, beta particles and gamma rays. The loss of mass from the nucleus changes the element to one of a lower mass. Carbon dating uses the decay of the 14C nucleus, a heavy and unstable isotope of carbon, to become the stable 14N isotope. The overall process is written ... 

C is naturally occurring, but is a radioactive (unstable) isotope. Its natural abundance is low enough not to be of concern in mass spectrometry, unless one makes special efforts, for example, using accelerator mass spectrometry. 

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