Physics
Nuclear Instability
Nuclear instability refers to the tendency of atomic nuclei to undergo spontaneous changes, such as radioactive decay or fission, in order to achieve a more stable configuration. This instability is often caused by an imbalance between the forces holding the nucleus together and the repulsive forces between protons. Unstable nuclei can release energy or particles as they transform into more stable forms.
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10 Key excerpts on "Nuclear Instability"
eBook - ePubChemistry
With Inorganic Qualitative Analysis
- Therald Moeller(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
8NUCLEAR CHEMISTRY
Publisher Summary
This chapter describes the forces within the nucleus, the conditions under which a nucleus becomes unstable and radioactive, and the relationship of nuclear stability to the abundance of the elements. It discusses the types of nuclear changes, such as α, ß, and γ decay, of natural radioactive elements. The chapter explains the bombardment reactions by which many radioactive isotopes and the synthetic elements can be synthesized. It illustrates the fission and fusion reaction. Nuclear fission and nuclear fusion bring nuclei into the area of greater stability by increasing the binding energy per nucleon. Nuclides above the stable nuclei curve undergo radioactive decay mainly by positron emission or electron capture. Nuclides below the stable nuclei curve undergo radioactive decay mainly by electron emission. The chapter describes the nuclear power plants in use at the present time and those that may become important in the future.In this chapter we look first at the forces within the nucleus, the conditions under which a nucleus becomes unstable and radioactive, and the relationship of nuclear stability to the abundance of the elements. Next we survey the types of nuclear changes— α, β and γ decay—of natural radioactive elements; the bombardment reactions by which many radioactive isotopes and the synthetic elements can be synthesized; and fission and fusion. Last, we describe the nuclear power plants in use at the present time and those that may become important in the future.The story of the discovery of radioactivity and the exploitation of nuclear energy holds more high drama than any other area of science. We think of Pierre and Marie Curie, reducing several tons of ore to a few specks of previously unknown radioactive elements. And carrying out this laborious task in a shed once used by a medical school for dissecting cadavers, a shed freezing and damp in the winter, and hot and stinking in the summer. There are the honors that came to Pierre and Marie and to their daughter, Iréne, and Iréne’s husband Frédéric Joliot-Curie who carried on the research; and there are the deaths of both Marie and Iréne from leukemia, quite likely caused by radiation from their own experiments
eBook - PDF- Allan Blackman, Steven E. Bottle, Siegbert Schmid, Mauro Mocerino, Uta Wille(Authors)
- 2022(Publication Date)
- Wiley(Publisher)
In this chapter, we will discuss some of the processes that occur in atomic nuclei. We will investigate why some nuclei are stable and some are radioactive, and we will detail some of the uses of radioactive materials. 27.1 Nuclear stability LEARNING OBJECTIVE 27.1 Define nuclear stability. As described in the introductory chapter on the atom, atomic nuclei can be divided into two types: stable and radioactive. Radioactive nuclei undergo spontaneous decay, and therefore we say that they are unstable. However, before we begin our discussion of nuclear stability, we must first define exactly what we mean by the word ‘stable’ in the context of an atomic nucleus. This is most easily done by defining its opposite, ‘unstable’. As an example, consider the radioactive neodymium nucleus Nd 144 60 . This has a half-life of 2.29 × 10 15 years. As we learned in the chapter on reaction kinetics, this means that any sample of this isotope decays by half over this period, and it will take ten half-lives, or 2.29 × 10 16 years, to decay essentially completely. These lengths of time, by our everyday standards, are almost incomprehensible; indeed they are about a million times the age of the universe! To our eyes, a sample of Nd 144 60 would show no obvious change and appear to be stable over the period of our lifetime. Despite this, we still say that the Nd 144 60 nucleus is unstable, even though its rate of decay is extremely slow. There are radioactive nuclei with half-lives of fractions of a second and others with half-lives of 10 19 years, but they are all unstable as they all undergo a nuclear process that results in their radioactive decay. Therefore, a stable nucleus is one in which such nuclear processes do not occur. One of the important factors that determines whether or not a particular nucleus is stable is the ratio of protons to neutrons in the nucleus.
- Martha Mackin(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
SEVENTEEN Nuclear chemistry OVERVIEW In previous chapters we studied chemical changes that occur as the result of changes in electron arrangements of atoms. In Chapter 17 we will study changes that occur in the nucleus of the atom. When the nuclei of unstable atoms disintegrate and give off radiation, the process is called radioactivity. These unstable atoms may occur in nature or may be produced artifically. This chapter defines the particles that are given off during the decay and explains how to write nuclear equations to represent the nuclear reactions that occur. Equations can be used to show the radioactive disintegration of both naturally occurring and artificial radioactive elements. They can also show the method by which artificial radioactive isotopes may be prepared. Half-life for radioisotopes is explained. Fission and fusion are nuclear changes in which mass is converted into large amounts of energy. Nuclear reactors utilizing fission produce heat energy, which is converted into electricity; fusion reactors are being developed as a commercial source of energy. Methods for and the units used in measuring radiation are included in the chapter. Various uses for radioisotopes, and the effects upon health of the radiation produced are also explained. **Specifics** 1. Definitions for the following terms should be learned: nuclear radiation accelerators radioactivity transuranium elements alpha radiation half-life beta radiation radiocarbon dating gamma radiation binding energy natural radioactivity fission radioactive disintegration series chain reaction artificial radioactivity critical mass radioisotopes breeder reactor neutron capture or fusion neutron activation radioactive tracer transmutation 470 Chapter 17 Topical Outline 471 2. General concepts that should be learned: CHAPTER 17 TOPICAL OUTLINE I. Description and interpretation of nuclear reactions 17.1 Radioactivity A.
eBook - PDFIsotopes in Nanoparticles
Fundamentals and Applications
- Jordi Llop, Vanessa Gomez-Vallejo, Jordi Llop, Vanessa Gomez-Vallejo(Authors)
- 2016(Publication Date)
- Jenny Stanford Publishing(Publisher)
In the latter state, the nucleus has an excess of internal energy and tends to move to a more stable state. The process by which the atomic nucleus moves from an unstable to a more stable state is called radioactive decay. Radioactive decay is spontaneous and is accompanied by the emission of particles and/or electromagnetic radiation. The unstable nucleus is called a radioactive atom or radionuclide. 145 During radioactive decay, the unstable atoms can become a different element via a process known as transmutation. This is the case in radioactive processes that result in the emission of alpha particles ( a , or 4 He 2+ ), electrons ( b – ), or positrons ( b + ). As an example, fluorine-18 ( 18 F) has nine protons and nine neutrons in its nucleus and is a positron emitter; on spontaneous decay a positron is emitted and, consequently, one of the protons becomes a neutron. The newly formed element, which has eight protons and ten neutrons, is oxygen-18 ( 18 O). Radioactive decay can also occur via electron capture (when a nucleus captures an orbiting electron, thereby converting a proton into a neutron with consequent transmutation), by emission of gamma ( g ) rays, by emission of a neutron, or by ejection of an orbital electron due to interaction with an excited nucleus in a process called “internal transition”. In the latter three decay modalities, the atoms before and after radioactive decay correspond to the same element because the number of protons remains unchanged and transmutation does not occur. Radioactive atoms exist in nature (and indeed are continuously produced naturally) and can be found in air, water, soil, or even living organisms. They can also be produced artificially using different technologies. Over 1500 radionuclides, both natural and artificial, have been identified. 6.2.2 Radioactive Decay Equations Radioactive decay is a stochastic process in which, according to quantum theory, it is impossible to predict when a specific atom will decay.
eBook - PDFRadioecology
Sources and Consequences of Ionising Radiation in the Environment
- R. J. Pentreath(Author)
- 2021(Publication Date)
- Cambridge University Press(Publisher)
Where more than one stable nuclide occurs, they are not equally abundant. In the case of hydrogen, for example, 99.985% are 1 H, the remaining 0.015% being 2 H. Tin, however, consists of 10 nuclides, the most abundant being 120 Sn (32.4%), 118 Sn (24.3%), and 116 Sn (14.7%) [1]. Some atomic nuclei are, or may be induced to become, unstable. Indeed, as the structure of the atom emerged from scientific observation it was conceptually difficult to understand how it had any stability at all, given that the positively charged protons at such close proximity within the nucleus of an atom should, on the understanding of physics at that time, repel each other and cause the nucleus to fall apart. To further complicate matters, it also became clear that the neutrons and protons were able to change from one to the other. It is now known that unstable nuclei disintegrate in a number of ways, and that their disintegration is always accompanied by the emission of some form of radiation. Such unstable nuclides are therefore known either as radioisotopes or by the almost synonymous term, radio- nuclide, when discussing a particular type of atom in a specific energy state. (And, again, this is the term that will mainly be used in the following chapters.) Such atoms, or the materials containing them, are therefore said to be radioactive, and the term used to describe this physical rather than chemical property of such atomic nuclei is radioactivity. Radioactivity is thus, as Becquerel had observed and as the term, coined by the Curies indicates, simply a phenomenon. But it is a phenomenon that has taken a long time to resolve, and in order to describe it one has to consider, briefly, something about the fundamental nature of forces and particles, which we are fortunately able to do thanks to what is currently known as the Standard Model. 2.2 Elementary Particles and Their Interactions So what is radioactivity, in a physical sense? Well, we now have a much better idea.
eBook - PDF- Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson(Authors)
- 2019(Publication Date)
- Openstax(Publisher)
During the beginning of the twentieth century, many radioactive substances were discovered, the properties of radiation were investigated and quantified, and a solid understanding of radiation and nuclear decay was developed. The spontaneous change of an unstable nuclide into another is radioactive decay. The unstable nuclide is called the parent nuclide; the nuclide that results from the decay is known as the daughter nuclide. The daughter nuclide may be stable, or it may decay itself. The radiation produced during radioactive decay is such that the daughter nuclide lies closer to the band of stability than the parent nuclide, so the location of a nuclide relative to the band of stability can serve as a guide to the kind of decay it will undergo ( Figure 21.5). FIGURE 21.5 A nucleus of uranium-238 (the parent nuclide) undergoes α decay to form thorium-234 (the daughter nuclide). The alpha particle removes two protons (green) and two neutrons (gray) from the uranium-238 nucleus. LINK TO LEARNING Although the radioactive decay of a nucleus is too small to see with the naked eye, we can indirectly view radioactive decay in an environment called a cloud chamber. Click here (http://openstax.org/l/16cloudchamb) to learn about cloud chambers and to view an interesting Cloud Chamber Demonstration from the Jefferson Lab. 21.3 • Radioactive Decay 1031 Types of Radioactive Decay Ernest Rutherford’s experiments involving the interaction of radiation with a magnetic or electric field ( Figure 21.6) helped him determine that one type of radiation consisted of positively charged and relatively massive α particles; a second type was made up of negatively charged and much less massive β particles; and a third was uncharged electromagnetic waves, γ rays. We now know that α particles are high-energy helium nuclei, β particles are high-energy electrons, and γ radiation compose high-energy electromagnetic radiation.
eBook - PDF- Richard L. Myers(Author)
- 2005(Publication Date)
- Greenwood(Publisher)
Every ele- ment has at least one unstable or radioactive isotope, but most have several. The nuclei of unstable isotopes undergo radioactive decay. Radioactive decay is the process where par- ticles and energy are emitted from the nuclei of unstable isotopes as they become stable. Nuclear Stability and Radioactivity Nuclear stability is related to the ratio of protons to neutrons. Protons packed into the atom's nucleus carry a positive charge and, therefore, exert a repulsive force on each other. In order for the nucleus to remain intact, the strong nuclear force (see chapter 11) must bal- ance the electrostatic repulsion between pro- tons. The strong nuclear force is the ''nuclear glue" responsible for holding the nucleus together. This force is related to the ratio of neutrons to protons in the nucleus. A normal hydrogen atom's nucleus contains a single proton; therefore, no neutrons are needed because there is no repulsive force between protons. All other elements have more than one proton and require neutrons to enable the strong nuclear force to interact. Helium atoms have two protons and two neutrons in their 208 Nuclear Physics Table 12.2 Nuclear Stability and Numbers of Neutrons and Protons Number of Neutrons Even Even Odd Odd Number of Protons Even Odd Even Odd Number of stable Isotopes 168 50 52 4 nuclei. The atomic number increases when moving up the periodic table because one pro- ton is added to the nucleus with each succes- sive element. When more protons are packed into the nucleus, more neutrons are required to overcome the resultant repulsive force. Stable isotopes prefer certain combina- tions of neutrons and protons. Most stable isotopes have an even number of both protons and neutrons. A smaller number of stable iso- topes have either an even number of protons and an odd number of neutrons or vice versa, and only a few have both an odd number of protons and neutrons (Table 12.2).
eBook - PDFChemistry
An Atoms First Approach
- Steven Zumdahl, Susan Zumdahl, Donald J. DeCoste, , Steven Zumdahl, Steven Zumdahl, Susan Zumdahl, Donald J. DeCoste(Authors)
- 2020(Publication Date)
- Cengage Learning EMEA(Publisher)
CHAPTER 21 CHAPTER 18 18.1 Nuclear Stability and Radioactive Decay Types of Radioactive Decay 18.2 The Kinetics of Radioactive Decay Half-Life 18.3 Nuclear Transformations 18.4 Detection and Uses of Radioactivity Dating by Radioactivity Medical Applications of Radioactivity 18.5 Thermodynamic Stability of the Nucleus 18.6 Nuclear Fission and Nuclear Fusion Nuclear Fission Nuclear Reactors Breeder Reactors Fusion 18.7 Effects of Radiation The Nucleus: A Chemist’s View A sunset view of a European nuclear power plant. (Tomas Sereda/iStockphoto.com) 727 Copyright 2021 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. S ince the chemistry of an atom is determined by the number and arrangement of its electrons, the properties of the nucleus are not of primary importance to chemists. In the simplest view, the nucleus provides the positive charge to bind the electrons in atoms and molecules. However, a quick reading of any daily newspaper will show you that the nucleus and its properties have an important impact on our society. This chapter considers those aspects of the nucleus about which everyone should have some knowledge. Several aspects of the nucleus are immediately impressive: its very small size, its very large density, and the magnitude of the energy that holds it together. The radius of a typical nucleus appears to be about 10 213 cm. This can be compared to the radius of a typical atom, which is on the order of 10 28 cm.
eBook - PDF- Philip Palin Dendy, Brian Heaton(Authors)
- 2011(Publication Date)
- CRC Press(Publisher)
1 1 Fundamentals of Radiation Physics and Radioactivity P P Dendy and B Heaton SUMMARY • Why some atoms are unstable is explained. • The processes involved in radioactive decay are presented. • The concepts of physical and biological half-life and the mathematical expla-nation of secular equilibrium are addressed. • The basic physical properties of X and gamma photons and the importance of the K shell electrons in diagnostic radiology are explained. • The basic concepts of the quantum nature of electromagnetic (EM) radia-tion and energy, the inverse square law and the interaction of radiation with matter are introduced. CONTENTS 1.1 Structure of the Atom ............................................................................................................ 2 1.2 Nuclear Stability and Instability ......................................................................................... 4 1.3 Radioactive Concentration and Specific Activity .............................................................. 6 1.3.1 Radioactive Concentration ....................................................................................... 6 1.3.2 Specific Activity ......................................................................................................... 7 1.4 Radioactive Decay Processes ................................................................................................ 7 1.4.1 β – Decay ....................................................................................................................... 7 1.4.2 β + Decay ....................................................................................................................... 7 1.4.3 α Decay ........................................................................................................................ 8 1.5 Exponential Decay .................................................................................................................
eBook - PDFChemistry
The Molecular Nature of Matter
- Neil D. Jespersen, Alison Hyslop(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
1006 CHAPTER 20 Nuclear Reactions and Their Role in Chemistry 20.4 Band of Stability Figure 20.10 plots all of the known isotopes of all of the elements, both stable and unstable, according to their numbers of protons and neutrons. The two curved lines in Figure 20.10 enclose a zone, called the band of stability, within which lie all stable nuclei. (No isotope above element 83, bismuth, is included in Figure 20.10 because none has a stable isotope.) Within the band of stability are also some unstable isotopes, because smooth lines cannot be drawn to exclude them. Any isotope not represented anywhere on the array, inside or outside the band of stability, probably has a half-life too short to permit its detection. For example, an isotope with 50 neu- trons and 60 protons would lie well below the band of stability and would likely be extremely unstable. Any attempt to synthesize it would likely be a waste of time and money. 135 130 125 120 115 110 105 100 95 90 85 80 Number of neutrons Number of protons 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 Key Stable nuclide, naturally occurring Unstable nuclide, naturally occurring Unstable nuclide, synthetic 20 8 2 50 82 28 Beta emitters Positron emitters 1n :1p 1.1n :1p 1.2n :1p 1.3n :1p 1.4n :1p 1.5n :1p 1n :1p Band of stability FIGURE 20.10 The band of stability. Stable nuclei fall within a narrow band in a plot of the number of neutrons versus the number of protons. Nuclei far outside the band are too unstable to exist. 20.4 Band of Stability 1007 Notice that the band curves slightly upward as the number of protons increases. The curva- ture means that the ratio of neutrons to protons gradually increases from 1:1, a ratio indicated by the straight line in Figure 20.10. This occurs because more protons require more neutrons to provide a compensating nuclear strong force and to dilute electrostatic proton–proton repulsions.
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