Unit_13_Nuclear_Chem Notes - Unit 13 Nuclear Chemistry Before nuclear power was used submarines could stay submerged for only brief periods of time A

Unit_13_Nuclear_Chem Notes - Unit 13 Nuclear Chemistry...

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Unformatted text preview: Unit 13 - Nuclear Chemistry 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, with a lump of nuclear fuel about 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 Radioactive Decay lab? 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. Review / Introduction Continued 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. • Uses: • Benefits: • Risks: 1, shows an element’s symbol with its atomic number and second way is to represent the nuclide by writing the followed by iNuclide Representation ts mass number, such as radium-228 or . It is not essential to include the atomic number when Nuclei represented two ways • ecause can be uclides of in n element have the same ide b all n a The symbol (X) shown with two numbers on the top and sotopes are atoms itshat have the same atomic number but bottom left of it. umbers. So, isotopes a(total # of protons and neutrons) numA = Mass number re nuclides that have the same ut different numbers of# of protons)The following symbols Z = Atomic number ( neutrons. Mass number of isotopes of tellurium. 122 52Te 124 52Te 128 52Te 70 neutrons 72 neutrons 76 neutrons of protons 52 are stable. protons 52 tellurium protons 52 So, their A X Z opes nuclei do not break usly. Yet, each of these nuclei are composed of 52 pnumber Atomic rothese positive charges exist so close together? Protons r because of their like charges. So, why don’t nuclei fall st be some attraction in the nucleus that is stronger than 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 alpha particle 4 He 2 beta particle (electron) 0 –1e or 4 ! 2 0 or –1" Symbol ! "– gamma radiation 0# 0 # neutron 1 0n n 1H 1 1 or 1p p 0 +1e 0 or +1" "+ proton positron Recall that the stability of a nucleus depends on the ratio of neutrons to protons, or the N/Z number. If a particular isotope has a large N/Z Beta Decay number or too many neutrons, the nucleus will decay and emit radiation. AConvertingn an unstable Protons may emit a high-energy electron, neutron i Neutrons into nucleus 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 called beta decay. This process often occurs in unstable nuclei that have emit a high-energy electron, called a beta particle. large N/Z numbers. beta decay 1 → 1 n +1 p 0 + −0 e 1 Because this process changes a neutron into a proton, the the atomic Because the process changes a neutron into a proton, atomic number umber of ucleus increases by one, as you can see in Figure 7. As a n of the n the nucleus increases by one. result of beta decay, carbon becomes a different element, nitrogen. However, the mass number does not change because the total number of – nucleons does not change as sbeta decay by the following equation. hown + 14 6C 14 6C 14N + −0 e →7 1 → 14 7N + beta particle Stabilizing Nuclei by Converting Protons into Neuetrons 0 −1 One way that a nucleus that has too many protons can become more sta- 14 6C → 14 7N + beta decay 0 −1e carbon-14 nucleus emits a beta particle, the carbon-14 nucleus changes into a nitrogen-14 nucleus. – + Electron Capture - Gamma Radiation 14 6C 14 7N → + beta particle 0 −1 e i n g N u c l e i b y C o nve r t i n g P ro t o n s i n t o N e u t ro n s S t a b i l i z i n g N u c l e i b y C o nve r t i n g N e u t ro n s i n t o P ro t o n s Recall that the stability of a nucleus depends on the ratio of neutrons to protons, or the N/Z number. If a particular isotope has a large N/Z number or too many neutrons, the nucleus will decay and emit radiation. A neutron in an unstable nucleus may emit a high-energy electron, called a beta particle ( particle), and change to a proton. This process is called beta decay. This process often occurs in unstable nuclei that have large N/Z numbers. beta particle If a nucleus has too many protons, it may become electron y that a nucleus that has too many protons cancapture anmore stafrom alled electron capture. In this process, the nucleus y a process cthe atom. absorbs This process atom’s ea proton into a neutronhe 1s ecreases one of the changes lectrons, usually from t and d orbital. cess changes a proton into a neutron andnumber stays he atomic the atomic number by one. The mass decreases t the same. by one. The mass number stays the same. beta decay 1 → 1 0 n +1 p + 0 −1e Because this process changes a neutron into a proton, the atomic number of the nucleus increases by one, as you can see in Figure 7. As a result of beta decay, carbon becomes a different element, nitrogen. However, the mass number does not change because the total number of nucleons does not change as shown by the following equation. 14 6C 1 +1 p + 0 −1e a charged electron emitted during a certain type of radioactive decay, such as beta decay gamma ray the high-energy photon emitted by a nucleus during fisson and radioactive decay Figure 8 Thunderstorms may produce terrestrial gamma-ray flashes (TGFs). 14N + −0 e →7 1 Stabi i g Nuclei by er electronlizcnaptureConv1ting Protons into Neutrons One way that a n that has too many protons can become more staucleus ble a p called electron capture. In this process, the nucleus is brocess → 0 n + ϒ y merely absorbs one of the atom’s electrons, usually from the 1s orbital. This process changes a proton into a neutron and decreases the atomic number by one. The mass number stays the same. l nucleus that decays by this process is chromium-51. 1 +1 p electron capture 0 + −0e → 1 n 1 A typical nucleus that decays by this process is chromium-51. 51 24Cr + 0 −1e ϒ = gamma rays electron capture +e 51 → V + final symbol in the e23V, indicates the release of gamma rays. T quation, + → he 51 24Cr 0 −1 electron capture 51 23 Many nuclear changes leave a nucleus in an energetic or excited state. When the nucleus stabilizes, it releases energy in the form of gamma rays. Figure 8 shows a thunderstorm during which gamma rays may also be produced. l symbol in the equation, , indicates the release of gamma rays. uclearWhen the lnucleus stabilizes,iit releases energyor the form state. changes eave a nucleus n an energetic in excited of gamma rays. he nucleus stabilizes, it releases energy in the form of gamma Nuclear Chemistr y Copyright © by Holt, Rinehart and Winston. All rights reserved. 649 PositroninEmissionssion Gamma Rays Are Also Emitted Positron Emi Some nuclei nucleiave too many protons protons an become stable by Some that h that have too many can become stable by emitting positrons, which positrons = the antiparticles ofThe process is similar to emitting are the antiparticles of electrons. electrons. electron capture in that a proton is changed into a neutron. However, in positron emission, a proton emits a positron. 1 +1 p positron emission 0 n + +0 e →1 1 Notice that when a proton changes into a neutron by emitting a positron, the mass number stays the same, but the atomic number decreases by one. The isotope chromium-49 decays by this process, as shown by the model in Figure 9. + 49 49 0 → 24Cr 23V + +1e Another example of an unstable nucleus that emits a positron is potassium-38, which changes into argon-38. positron 49 24 Cr → 38 19K → 38 18Ar 49 23 0 V + +1e + 0 +1 e The positron is the opposite of an electron. Unlike a beta particle, a positron seldom makes it into the surroundings. Instead, the positron usu- tromagnetic radiation Nuclear changes can be easier to understand than chemical changes because only a few types of nuclear changes occur. One type is the sponTable taneous 1 haCge racanruststablef nuuleus ro arrm la s ane stabls one. This c n ha of te i n ics o N cclea t Pfo tic e mord Ray e change involves tMass eamu) e of particles, electromagneticStoppedsbyor both he r ( leas wave , Particle Charge Symbol and is generally called radioactivity or rad+ oacti1 e decay. Specifically, i v a few Proton 1.007 276 47 +1 p, p , +1 p, 1H radioactivity is the spontaneous breakdown of u1nstable nuclei sheetsoduce to pr of paper particles or energy. Table 1 summarizes the properties of both the particles a Neutron nerg release 6 b 9 r 1.008 n 01 and the ecanydecay d64y 0 adioa0 tive dan, y. , 0 n (α) pfew centic eca n nuclei by emitting alpha article Alpha Particle Emission activity rocess by which an unstable eus emits one or more partior energy in the form of romagnetic radiation ww.sci links.org Unstable , article 0.000 48 80 −1 Stabilizing Nuclpei by Losing 5Al5pha Particl,es pic: Radioactive Decay i Links code: HW4106 − meters of lead 0 −1e* a few sheets of Table 1 Characteristics of Nuclear Par ticles and aluminum foil Rays (electron) An unstable nucleus that has an N/Z number that is much larger than 1 +0 Positron† 0.000 amu) +1 , +1e* same as by Particle Mass (548 580 Charge Symbol Stopped electron can decay by emitting an alpha particle. In addition,4 none of the elements 2+ 1 skin or heets particle 4.001 474 47 +2 2 a few s one Proton 1.007 276 92 +1 p, p+, , 1He H , +1 p, 1 that have atomic(He-4 nucleus) greater than 83 and mass numberspgreater than numbers sheet of paper of aper Gamma 0 0 several cdecay by enti209 have stable Neutron ray . So1.008 664 90of these unstable isotopes entiisotopes , many 1 a few c 0 n, n0, 0 n of lead meters of l d Atomic number decreases a by and mass numbermetersetaead ecay emitting alpha particles, as well bys two electron capture odecreases . rb ww.sci links.org − E ecay ic: Radioactive Dmissions , 1* a f not mean particle 1 by 4. Uranium-238 is one sexample0.000 5he symbols f−or electron, and−0eositron doesew sheets of . in t 48 580 *The uperscript zero p HW4107 i Links code: HW4106 (electron)have zero mass. It means their mass number is zero. aluminum foil that they alpha decay 40 238 Positron† U is the 580 of the 1 lectron. Each* article has an antiparticle, same as electron 0.000 548 234 Th + +, He antiparticle→ + 0 †The positron 2 +1e p 92 9e butarticle he positron is frequently involved in nuclear4changes. skin or one p only t 4.001 474 92 +2 , 2+, He 2 Notice that the a(tomic number in the equation decreases by twof while the He-4 nucleus) sheet o paper Chapter 18 ) mass Many heavy metals ylike Uraniump0articles©throughndaWeveralll crphenetratnumber decreases b ( four. Alpha -238Copgiot hyaveinevaerysiseries tsoferved. low enti-s Gamma ray 0 yr gh b Holt, R h rt a nston. A ig re reactions called a decay lseries. nd soon collide with meters of leadatter. ing ability because they are arge a other m ww.sci links.org ic: Radioactive Emissions to external sources of alpha radiation is usually harmless. Exposure *The superscript zero in the symbols for electron and positron does not mean Links code: HW4107 that they that undergo alpha decay are ingested or inhaled, However, if substanceshave zero mass. It means their mass number is zero. series before they reach a stable state. The decay series for uranium-238 is shown in Figure 10. After the 238U nucleus decays to 234Th, the nucleus is 92 90 still unstable because it has a large N/Z number. This nucleus undergoes beta decay to produce 234Pa. By another beta decay, 234Pa changes 91 91 234 to 92U. After a number of other decays (taking millions of years), the nucleus finally becomes a stable isotope, 206Pb. 82 Decay Series Example Figure 10 Uranium-238 decays to lead-206 through a decay series. Uranium-238 Decay Series 242 238 92 U 238 4.5 X 109 y 234 90 Th 24.1 d 234 230 90 Th 230 Mass number 234 234 91 Pa 92 U 1.2 min 2.5 X 105 y 7.5 X 104 y 226 88 Ra 1599 y 226 222 86 Rn 3.8 d 222 218 218 84 Po 3.0 min 214 214 214 214 82 Pb 83 Bi 84 Po 27 min 19.9 min 163.7 µs . 210 210 81 Tl 1.3 min 210 82 Pb 22.6 y 206 206 81 Tl 4.2 min 82 s min d y 206 82 Pb stable 81 218 85 At 1.6 s 202 80 210 83 Bi 5.01 d 210 84 Po 138.4 d 83 84 85 86 87 88 89 = = = = = = seconds minutes days years alpha decay beta decay 90 91 92 93 Atomic number Nuclear Chemistr y Copyright © by Holt, Rinehart and Winston. All rights reserved. 651 series. Decay Series α-decay 234 90 Th 24.1 d 7.5 X 104 y 4.5 X 109 y 234 234 91 Pa 92 U 1.2 min 2.5 X 105 y β-decay 230 90 Th 238 92 U β-decay Table N Selected Radioisotopes Nuclide Half-Life Decay Mode Nuclide Name 198Au 2.69 d !– gold-198 14C 5730 y !– carbon-14 37Ca 175 ms !+ calcium-37 60Co 5.26 y !– cobalt-60 137Cs 30.23 y !– cesium-137 53Fe 8.51 min !+ iron-53 220Fr 27.5 s " francium-220 12.26 y !– hydrogen-3 8.07 d !– iodine-131 37K 1.23 s !+ potassium-37 42K 12.4 h !– potassium-42 10.76 y !– krypton-85 7.2 s !– nitrogen-16 19Ne 17.2 s !+ neon-19 32P 14.3 d !– phosphorus-32 239Pu 104 y " plutonium-239 226Ra 1600 y " radium-226 222Rn 3.82 d " radon-222 90Sr 28.1 y !– strontium-90 99Tc 105 y !– technetium-99 1.4 × 1010 y " thorium-232 y " uranium-233 7.1 × 108 y " uranium-235 " uranium-238 3H 131I 85Kr 16N s 232Th 233U r e ow lue o pink Spontaneous/Natural Transmutation 235U 238U 2.44 × 2.13 × 1.62 × 4.51 × 105 109 y ms = milliseconds; s = seconds; min = minutes; h = hours; d = days; y = years Decay reactions that do not require an outside energy source to proceed are considered spontaneous and natural. • One atom on the left hand side of the reaction • Forms multiple particles Artificial Transmutation Decay reactions that need an external energy source to proceed are considered artificial. • Multiple atom/particle on the left hand side of the reaction • Forms multiple particles or a single product (1) the conversion of mass to nuclear bind(1) protons and containsnergy. electrons ing e (2) neutrons a and (1) 91cprotonsnd electronsaw of conserva(2) a ontradiction t140 neutrons. o the l (3) protons and nd 140 e (2) 91 protons aneutrons lectrons. tion of mass. (4) protons, neutrons and (3) miscalculation of 140 protons. p t ass of a (3) 91 neutrons and , he melectrons roton. (4) 91 neutrons and 140 mass of a . eutron. 3.(4) hich symbol representselectronsnwith 16 W miscalculation of the a nuclide (4) heaviest subatomic parti contains of cesium-137. (1) neutrons to protons in a 18. Which positrons most likely i (1) isotope neutrons in a (2) fuelprotons to reaction? for a fission (2) cesium-136 (3) neutrons to protons in a (1) oxygen-18 (4) (3) beta particle neutrons to protons in a (2) hydrogen-3 (4) 1 ratio. particle to alpha (3) calcium- 41 (4) uranium-235 following 9.31.hich combination of prot W Examine the Section Review protons and 11 Which any n18 neutrons? present in a 24. .How mGroup 16 element has no stablen atom ucleons are 34 34 isotope? (1) 16 Se (3) 16 S of thorium-232? (3) Te 16 ((1) 323 1) O Se (3)18 S (2) S (4) P232 18 (2) (4) 16 o (2) 90 (4) 142 4. Protons and neutrons are made u c of 12. Which radioactive emission has a pharge of 25. Compared to a carbon-12 nucleus, a ( 2 electrons. (3) +1) and a mass of 4 amu? nucleons. c(1) alpha pnucleus has(4) positron arbon-14 article two (2) positrons. (3) quarks. (1) fewer protons. (3) more neutrons (4) are radioactive . 5. (2) beta particle Samples of elements that gamma ray (2) more protons. with fewer neutrons. (4) must contain atoms mission is deflected 13. Which radioactive e (1) stable n negative e an alpha a magnetic 26. When an atom emitslectrode inparticle, its toward the uclei. (2) unstable n field? mass number uclei. (3) an even (1) positron number of nucleons per nucleus. (1) decreases by 2. (3) decreases by 4. (4) an e particle (2) betaven mass number. increases by 4. (2) increases by 2. (4) (3) electron 27. Which radioactive isotope emits an alpha (4) gamma ray particle? 14. The changing of a nucleus by bombardment (1) iron-53 neutron he major obstacle u ields a n 131 19. What is tnumber yI 131 X → 53 54 stable? nuclei to form a single nucle (1) What ize of the uclei even/even (1) small sparticle isnrepres (2) even/odd (2) small mass of the nuclei (1) proton (3) odd/even (3) repulsion of the nuclei (2) neutron (4) number of neutrons in t (4) odd/odd 32. What does X represen 20. What are twoquation? tha nuclear e properties isotope that is used in medi X 198Hg → 80 must have? (1) short half-life and be qu 198 (1) 81 Tl from the body. Keeping a positive attitude d 198 (2) long hfAu on nd be quin (2) 79 ocus help you alf-life a the test a from the your score. body. 33. short half-life andrbe slo (3) Which equation epres from the body. 4 2 2 (1) 1 H + 1 H 2 He ar → + (4) long half-life and Nucse be l low (1) (2) (3) (4) electron capture. nuclear fusion. beta decay. gamma release. Section Review 29. Examine the following nuclear equation. 14 6C → 14 N + −0 e 7 1 This radioactive decay is an example of (1) positron emission. (2) beta decay. (3) electron capture. (4) alpha decay. u obest ndan. on. 17. Which describes a positron? (1) same mass and charge as an electron (2) mass of a proton and a +1 charge Copyright (3) Holt, Rinehar t and Weston. All rights reser ved. +1 charge © by mass of an in lectron and a (4) heaviest subatomic particle 18. Which isotope is most likely to be used as a fuel for a fission reaction? (1) oxygen-18 (2) hydrogen-3 (3) calcium- 41 nuclear equation? X 222Rn + 4 He → 86 2 (1) 226 88 Rn (3) 222 88 (2) 218 84 Po (4) 222 86 35. What type of nuclear reactio sented by the following equa 235 92 U (1) (2) (3) (4) + 1 n 139Ba + 94 Kr + 3 → 56 0 36 nuclear fusion natural radioactive decay decomposition nuclear fission Nuclear C y one. The mass number stays the same. e Also Emitted in Positron Emission electron capture 1 ave too many p rotons canecome stable by emitting p + −0e b 1 n →0 +1 1 Section Reviewsimilar to e the antiparticles of electrons. The process is nucleus phat decays by reactionrocesseutron. However, in t roton is changed nto a n s chromium-51. that aWhat kind of nuclear this ip is shownibelow? electron a proton emits a positron. capture 51 51 0 24Cr + −1e → 23V + positron emission 0 n + +0 e alpha-decay→ 1 (1) 1 symbol in the equation, , indicates the release of gamma rays. (2) beta-decay lear changes leave a a ucleus inbanemitting a positron, state. proton changes into n neutron y energetic or excited (3) positron emission nu tleusame, iliz hetare s electron i tomic number d in the f by o of ays che s(4)tabbutets,captureleases energy ecreases orm ne. gamma e 8 sho ds a th by t rst p m dur as which by the rays m ium-49 wecaysundehis orrocess,ing shown gamma model ay also ed. Below is an example of: 1 +1...
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