C H A P T E R Before nuclear power was used, submarines could stay submerged for only brief periods of time. A diesel-powered sub had to surface regularly to refuel and recharge its batteries. However, 640 with a lump of nuclearCopyright © by Holt, Rine harfuelt and Winston. All rights r eseaboutrved. the size of a golf ball, the first nuclear-powered sub could remain underwater for months and travel about 60,000 miles. Today, subs only need to refuel about once every 9 years. Chapter Objectives - Nuclear Chemistry Review & Atomic Nuclei Rutherford’s Gold Foil Experiment - Nucleons Nuclide Representation Nuclear Change Radioactive Decay Natural/Artificial Transmutation Nuclear Fission & Fusion Half-Life Nuclear Energy & Waste Uses of Nuclear Chemistry Medical, Dating, Power Chapter Test, Homework, etc. Section 1 – Review & Atomic Nuclei Rutherford’s Gold Foil Experiment – determined charge and mass distribution in an atom – 99% of an atom’s mass is in the nucleus, but makes up less than 1% volume – atoms are composed of protons, electrons, and neutrons – protons and neutrons are located in the nucleus of the atom and are called nucleons. – the nucleus has a positive charge. Nuclear Chemistry • Concerned with chemistry taking place in the nuclei of atoms • Stability of nuclei depends on the number of protons and neutrons in their nuclei. S E C T I O N Atomic Nuclei 1 and Nuclear Stability KEY TERMS OBJECTIVES • nucleons 1 Describe how the strong force attracts nucleons. • nuclide 2 Relate binding energy and mass defect. • strong force • mass defect 3 Predict the stability of a nucleus by considering factors such as nuclear size, binding energy, and the ratio of neutrons to protSoEnsC iTn IthOeN nucleus. Atomic Nuclei Nuclear Forces 1 and Nuclear Stability In 1911, Ernest Rutherford’s famous gold-foil experiment determined the TTopicopic LinkLink distribution of charge and mass in an atom. Rutherford’KEYsT EresultsRMS showed OBJECTIVES Refer to the “Atoms and Moles” that all of an atom’s positive charge and almost all of• nucleonsits mass are con-1 Describe how the strong force attracts nucleons. chapter for a discussion of • nuclide tained in an extremely small nucleus. 2 Relate binding energy and mass defect. Rutherford’s experiment. • strong force Other scientists later determined more details about• mass defect the nuclei of3 Predict the stability of a nucleus by considering factors such as nuclear size, binding energy, and the ratio of neutrons to protons in the nucleus. nucleon atoms. Atomic nuclei are composed of protons. The nuclei of all atoms except hydrogen also are composed of neutrons. The number of protons a proton or a neutron Nuclear Forces is the atomic number, Z, and the total number of protons and neutrons isIn 1911, Ernest Rutherford’s famous gold-foil experiment determined the Topic Link the mass number, A.The general symbol for the nucleus of an atom of ele-distribution of charge and mass in an atom. Rutherford’s results showed Refer to the “Atoms and Moles” that all of an atom’s positive charge and almost all of its mass are con- chapter for a discussion of tained in an extremely small nucleus. nuclide ment X is shown in Figure 1. Rutherford’s experiment. Other scientists later determined more details about the nuclei of The protons and neutrons of a nucleus are called nucleons. A nuclide an atom that is identified by the nucleon atoms. Atomic nuclei are composed of protons. The nuclei of all atoms except hydrogen also are composed of neutrons. The number of protons is a general term applied to a specific nucleus with a givena proton number or a neutron of pro- number of protons and neutrons is the atomic number, Z, and the total number of protons and neutrons is in its nucleus tons and neutrons. Nuclides can be represented in two ways. One way,the mass number, A.The general symbol for the nucleus of an atom of ele- nuclide ment X is shown in Figure 1. shown in Figure 1, shows an element’s symbol with its atomic number and The protons and neutrons of a nucleus are called nucleons. A nuclide an atom that is identified by the mass number. A second way is to represent the nuclidenumber by of protons writing and neutrons theis a general term applied to a specific nucleus with a given number of pro- in its nucleus tons and neutrons. Nuclides can be represented in two ways. One way, element’s name followed by itsNuclide mass number Representation, such as radium-228 orshown in Figure 1, shows an element’s symbol with its atomic number and Figure 1 einsteinium-253. It is not essential to include the atomic number whenmass number. A second way is to represent the nuclide by writing the In this figure, X represents Nuclei can be represented in two ways element’s name followed by its mass number, such as radium-228 or • Figure 1 einsteinium-253. It is not essential to include the atomic number when showing a nuclide because all nuclides of an elementIn this have figure, X therepresents same the element, Z represents showing a nuclide because all nuclides of an element have the same The symbol (X) is shown with two numbers on thethe element,top andZ representsbottom the atom’s atomic number, atomic number. the atom’s atomic number, atomic number. and A represents the Recall that isotopesleft ofare it. atoms that have the same atomicand A represents number the but Recall that isotopes are atoms that have the same atomic number but A = Mass number (total # of protons and neutronselement’) s mass number. different mass numbers. So, isotopes are nuclides that have the same num- element’s mass number. different mass numbersZ. So= At,omicisotopes number are (# of nuclides protons) that have the same num-ber of protons but different numbers of neutrons. The following symbols Mass number ber of protons but different numbers of neutrons. The following symbolsrepresent nuclei of isotopes of tellurium. 122Te 124Te 128Te Mass number represent nuclei of isotopes of tellurium. A 52 52 52 These three isotopes of tellurium are stable. So, their nuclei do not break 122 124 128 down spontaneously. Yet, each of these nuclei are composed of 52 pro- 52Te 52Te 52Te tons. How can these positive charges exist so close together? Protons A 70 neutrons 72 neutrons 76 neutrons X repel each other because of their like charges. So, why don’t nuclei fall Z apart? There must be some attraction in the nucleus that is stronger than These three isotopes of tellurium are stable. So, their nuclei doAtomic not number break 52 protons 52 protons 52 protons the repulsion due to the positive charges on protons. down spontaneously. Yet, each of these nuclei are composed of 52 pro- 642 Chapter 18 tons. How can these positive charges exist so close together? Protons Copyright © by Holt, Rinehart and Winston. All rights reserved. X repel each other because of their like charges. So, why don’t nuclei fall Z apart? There must be some attraction in the nucleus that is stronger than Atomic number the repulsion due to the positive charges on protons. 642 Chapter 18 Copyright © by Holt, Rinehart and Winston. All rights reserved. Nuclide Representation #2 The element name is given followed by the Mass Number Radium-228 or Ra-228 Nuclei that have mass numbers greater than 209 and atomic numbers greater than 83 are never stable. Section 2 – Objectives Radioactive Decay Stabilizing unstable nuclei Nuclear particle and ray emission (α, β, positrons, ϒ-rays) Balancing nuclear equations Natural & Artificial Transmutation Nuclear Fission & Fusion What takes place? Chain Reactions in Nuclear Reactors Half-Life Nuclear Energy and Waste Section 2 – Nuclear Change Radioactive Decay - Only a few types of nuclear changes occur. Radioactivity - the process by which an unstable nucleus emits one or more particles and energy in the form of electromagnetic energy to make a more stable nucleus. Table O Symbols Used in Nuclear Chemistry Name Notation Symbol 4 4 alpha particle 2He or 2! ! 0 0 – beta particle (electron) –1e or –1 " " 0 gamma radiation 0# # 1 neutron 0n n 1 1 proton 1H or 1p p 0 0 + positron +1e or +1 " " Table P Organic Prefixes Prefix Number of Carbon Atoms meth- 1 eth- 2 prop- 3 but- 4 pent- 5 hex- 6 hept- 7 oct- 8 non- 9 dec- 10 Table Q Homologous Series of Hydrocarbons Examples Name General Formula Name Structural Formula H H alkanes CnH2n+2 ethane H C C H H H H H alkenes CnH2n ethene C C H H alkynes CnH2n–2 ethyne H C C H n = number of carbon atoms 6 Reference Tables for Physical Setting/CHEMISTRY Figure 7 When the unstable carbon-14 nucleus emits beta decay – a beta particle, the + carbon-14 nucleus changes into a nitrogen-14 nucleus. 14 14 beta particle 6 C → 7 N + 0 −1e Stabilizing Nuclei by Converting Neutrons into Protons Recall that the stability of a nucleus depends on the ratio of neutrons beta particle to protons, or the N/Z number. If a particular isotope has a large N/Z a charged electron emitted number or too many neutronsBeta, the nucleus Deca willy decay and emit radiation. during a certain type of AConver neutronting inN eutronsan unstable into Prot nucleusons may emit a high-energy electron, radioactive decay, such as beta decay called a beta particle (␤ particle), and change to a proton. This process is If an isotope has too many neutrons, the nucleus will decay and emit a called beta decay. This process often occurs in unstable nuclei that have gamma ray high-energy electron, called a beta particle.