Chemistry - an illustrated guide to science (794128), страница 32
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These can be raised orlowered as needed to control thenuclear reaction. The control rods aremade of alloys that absorb neutrons.When they are lowered, moreneutrons are absorbed.● The heat produced by the fissionreaction is removed through a heatexchanger.
The loop between thenuclear reactor and the heatexchanger is sealed so there is nodanger of radioactive material escapinginto the environment.● The heat is used to convert water intopressurized steam. The high pressuresteam drives a turbine connected to agenerator, which produces electricity.© Diagram Visual Information Ltd.● Uran iu m ,186RADIOACTIVITYThe uranium seriesTlKey wordsalpha particleatomic numberbeta particledaughter nucleushalf-lifePbBiPoAtRnFrRaAcThPaU240mass numbernuclideradioactive decayuraniumuranium series4.5 × 10 9 aRadioactive decay1.18m235● Radioactivenuclei break down by aprocess known as radioactive decayin order to become more stable.
In aradioactive decay series, each memberof the series is formed by the decay ofthe n u clide before it until a stablenuclide is produced. As the nucleidisintegrate, they emit alpha (!) orbeta (") particles.● There are three naturally occurringradioactive decay series: the u ran iu mseries, the actinium series, and thethorium series. Each ends with a stableisotope of lead.24.1d2.5 × 10 5a2308.0 × 10 4 a2251620aThe uranium seriesuranium series involves theradioactive decay of U-238 to stablePb-206.
It is also known as the 4n+2series (where n is an integer), becauseeach member of the series has a massequivalent to 4n+2 .● The graph indicates how the decayoccurs. Atom ic n u m bers are plottedon the x-axis. The m ass n u m bers areon the y-axis. The symbol for theelement is at the top of the graph.Each diagonal line represents an alpha(!) decay; each horizontal line a beta(") decay. A circle indicates thedau ghter n u cleu s (the nucleusproduced by the decay of the previousnucleus).
Half-life is indicated in years(a), days (d), hours (h), minutes (m),and seconds (s).Mass number● The3.82d2203.05m3.05m1.5s21519.7m26.8m1.6 × 10 –4 s19.7m22a5.0d210α1.32m5.0d138.3d© Diagram Visual Information Ltd.Decay chainU-238 ➞ Th-234 ➞ Pa-234 ➞ U-234 ➞Th-230 ➞ Ra-226 ➞ Rn-222 ➞ Po-218 ➞At-218 ➞ Pb-214 ➞ Bi-214 ➞ Po-214 ➞Ti-210 ➞ Pb-210 ➞ Bi-210 ➞ Po-210 ➞Pb-206 (stable)β4.2m2052008081828384858687Atomic number8889909192187The actinium seriesTlPbBiPoAtRnFrRaAcRADIOACTIVITYThPaU240Key wordsactiniumactinium seriesalpha particleatomic numberbeta particledaughter nucleushalf-lifemass numbernuclideradioactive decayRadioactive decay235● Radioactivenuclei break down by aprocess known as radioactive decayin order to become more stable.
In aradioactive decay series, each memberof the series is formed by the decay ofthe n u clide before it until a stablenuclide is produced. As the nucleidisintegrate, they emit alpha (!) orbeta (") particles.● There are three naturally occurringradioactive decay series: the uraniumseries, the actin iu m series, and thethorium series.
Each ends with a stableisotope of lead.7.1 × 10 8 a24.6h2303.43 × 10 4 a22.0 a22518.6d22.0 aThe actinium series● Theactinium series involves theradioactive decay of U-235 to stablePb-207. It is also known as the 4n+3series (where n is an integer), becauseeach member of the series has a massequivalent to 4n+3.● The graph indicates how the decayoccurs. Atom ic n u m bers are plottedon the x-axis. The m ass n u m bers areon the y-axis. The symbol for theelement is at the top of the graph.Each diagonal line represents an alpha(!) decay; each horizontal line a beta(") decay. A circle indicates thedau ghter n u cleu s (the nucleusproduced by the decay of the previousnucleus).
Half-life is indicated in years(a), days (d), hours (h), minutes (m),and seconds (s).11.2d2203.92s1.83 ×10 –3s21510 –4 s2.16m21036.1mα0.52s2.16mDecay chain4.2mU-235 ➞ Th-231 ➞ Pa-231 ➞ Ac-227 ➞Th-227 ➞ Fr-223 ➞ Ra-223 ➞ Rn-219 ➞Po-215 ➞ At-215 ➞ Pb-211 ➞ Bi-211 ➞Po-211 ➞ Tl-207 ➞ Pb-207 (stable)β20520 08081828384858687Atomic number8889909192© Diagram Visual Information Ltd.Mass number21m188RADIOACTIVITYThe thorium seriesTlKey wordsalpha particleatomic numberbeta particledaughter nucleushalf-lifePbBiPoAtRnFrRaAcThPaU9192240mass numbernuclideradioactive decaythoriumthorium seriesRadioactive decay235● Radioactivenuclei break down by aprocess known as radioactive decayin order to become more stable.
In aradioactive decay series, each memberof the series is formed by the decay ofthe n u clide before it until a stablenuclide is produced. As the nucleidisintegrate, they emit alpha (!) orbeta (") particles.● There are three naturally occurringradioactive decay series: the uraniumseries, the actinium series, and thethoriu m series. Each ends with a stableisotope of lead.1.39 × 10 10 a2306.13h6.7a1.90 a225The thorium series● The3.64dMass numberthorium series involves theradioactive decay of Th-232 to stablePb-208. It is also known as the ( 4n)series (where n is an integer) becauseeach member of the series has a massequivalent to 4n.● The graph indicates how the decayoccurs. Atom ic n u m bers are plottedon the x-axis. The m ass n u m bers areon the y-axis.
The symbol for theelement is at the top of the graph.Each diagonal line represents an alpha(!) decay; each horizontal line a beta(") decay. A circle indicates thedau ghter n u cleu s (the nucleusproduced by the decay of the previousnucleus). Half-life is indicated in years(a), days (d), hours (h), minutes (m),and seconds (s).22054.5s2150.16s47m10.6h2103.0 × 10 –7s47mα3.1m© Diagram Visual Information Ltd.Decay chainTh-232 ➞ Ra-228 ➞ Ac-228 ➞ Th-228 ➞Ra-224 ➞ Rn-220 ➞ Po-216 ➞ Pb-212 ➞Bi-212 ➞ Po-212 ➞ Tl-208 ➞Pb-208 (stable)β20520 08081828384858687Atomic number888990189The neptunium seriesTlPbBiPoAtRnFrRaAcThPaURADIOACTIVITYNpPuAmalpha particleatomic numberbeta particledaughter nucleushalf-life245PuAmmass numberneptuniumneptunium seriesnuclideradioactive decayRadioactive decay● Radioactivenuclei break down by aprocess known as radioactive decayin order to become more stable.
In aradioactive decay series, each memberof the series is formed by the decay ofthe n u clide before it until a stablenuclide is produced. As the nucleidisintegrate, they emit alpha (!) orbeta (") particles.● The n eptu n iu m series is composed ofisotopes that do not occur in nature.240UNp235PaU230The neptunium seriesThRa225● Theneptunium series starts with theartificial isotope plutonium-241 andends with bismuth-209.
Each memberof the series has a mass equivalent to4n+1 (where n is an integer).● The graph indicates how the decayoccurs. Atom ic n u m bers are plottedon the x-axis. The m ass n u m bers areon the y-axis. The symbol of theelement is at the top of the graph.Each diagonal line represents an alpha(!) decay; each horizontal line a beta(") decay. A circle indicates thedau ghter n u cleu s (the nucleusproduced by the decay of the previousnucleus).AcFr220At215BiDecay chainPoPu-241 ➞ Am-241 ➞ Np-237 ➞ Pa-233 ➞U-233 ➞ Th-229 ➞ Ra-225 ➞ Ac-225 ➞Fr-221 ➞ At-217 ➞ Bi-213 ➞ Po-213 ➞Pb-209 ➞ Bi-209 (stable)α210TlPbBiβ20520 080818283848586878889Atomic number909192939495© Diagram Visual Information Ltd.Mass numberKey words190RADIOACTIVITYKey wordsalpha decayalpha particleatomic numberbeta decaybeta particlegamma radiationground statekinetic energymass numbernuclideRadioactivity of decaysequences1 Alpha decayAZ1 Alpha decay● Alphadecay is the process in whichthe nucleus of an atom emits an alphaparticle (which has the same structureas the helium-4 nucleus: 24He).● The new atom’s atomic m ass n u m ber( A) is reduced by 4 and its atom icn u m ber ( Z) is decreased by 2.● Uranium-238 decays to thorium-234 bythe loss of an alpha particle.● Energy is also released as gam m a (!)radiation .XYZ–2238+234"U922He+!He+!4Th +902Example of alpha decay: uranium decay to thorium2 Alpha particle spectruma"e"e"eb!● Thegrou n d state of the uraniumnucleus (the natural state of the lowestenergy of the nucleus) is at a higherenergy than the ground state of thethorium nucleus.● Some energy is released in the form ofkin etic en ergy, which is carried by thealpha particle.● The remaining energy is released asgamma radiation.f"ec!fd3 Beta decayA3 Beta decayZ● Betadecay is the process in which thenucleus of an atom emits a betaparticle (an electron).● The new atom’s atomic number ( Z) isincreased by 1, while the atomic massnumber ( A) remains unchanged.● Thorium-234 decays to protactinium234 by the loss of a beta particle.
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