Chapter 18: Radioactivity & Nuclear Reactions
Chapter 18: Radioactivity& Nuclear Reactions Radioactivity Types of Radiation Nuclear Reactions Half Life
Radioactivity The word radioactivitywas first used in the 1890s byMarie Curie. She used the word radioactivity to describethe property of certain substances to giveoff invisible “radiations” that could bedetected by films.
Radioactivity We now know thatradioactivity comes from thenucleus of the atom. If the nucleus has too manyneutrons, or is unstable forany other reason, the atomundergoes radioactivedecay.
Radioactivity Unstable atoms will continue to undergoradioactive decay until they form stable atoms.(Change into atoms of another element.) The word decay means to "break down.” Radioactive decay gives off energy.
Nuclear Reactions and Energy A nuclear reaction is any process that changesthe nucleus of an atom. Radioactive decay is one form of nuclearreaction.
Types of Radiation Scientists quickly learned thatthere were 3 different kinds ofradiation given off by radioactivematerials. The scientists called them “rays”because the radiation carriedenergy and moved in straight lines,like light rays.
Types of Radiation In Alpha decay, the nucleus ejects two protons andtwo neutrons. Beta decay occurs when a neutron in the nucleussplits into a proton and an electron. Gamma decay is not truly a decay reaction in thesense that the nucleus becomes something different.
Alpha RadiationAn alpha particle isequivalent to a helium-4nucleusThis is anexampleof a nuclearequation.It decayed to an alphaparticle and U-235.This is the original“unstable” atom.Number of ProtonsNumber of Protons
Fusion Reactions A fusion reaction is anuclear reaction thatcombines, or fuses, twosmaller nuclei into a largernucleus. It is difficult to make fusionreactions occur becausepositively charged nucleirepel each other.
Fission reactions A fission reaction splits upa large nucleus into smallerpieces. A fission reaction typicallyhappens when a neutronhits a nucleus with enoughenergy to make the nucleusunstable.
Examples of fusion and fission.FUSIONFusion is the process thattakes place in stars like ourSun. Whenever we feel thewarmth of the Sun and seeby its light, we areobserving the products offusion.FISSIONFission is used to produceenergy for nuclear bombs,but we also use fissionpeacefully everyday toproduce energy in nuclearpower plants
Half-Life The “half-life” (h) is the time it takes forhalf the atoms of a radioactive substance to decay. For example, suppose we had 20,000 atoms of aradioactive substance. If the half-life is 1 hour,how many atoms of that substance would be left .Time#atomsremaining% of atomsremaining1 hour (one lifetime) ?10,000(50%)2 hours (two lifetimes) ?5,000(25%)3 hours (three lifetimes) ?2,500(12.5%)
Half-Life Practice1. What is the percentage of radioactivenuclei left after 3 half-lives pass?2. The half-life of Rn-222 is 3.823 day. Ifthe original mass of a sample of thisisotope is 0.20 g, how much of it remainsafter 7.646 days?
Half-Life GraphNotice howthe decays arefast andfurious at thebeginning andslow downover time
What is the half life of this isotope?
Decay Chain
Half-Life The “half-life” (h) is the time it takes for half the atoms of a radioactive substance to decay. For example, suppose we had 20,000 atoms of a radioactive substance. If the half-life is 1 hour, how many atoms of that substance would be left .
Nuclear Chemistry What we will learn: Nature of nuclear reactions Nuclear stability Nuclear radioactivity Nuclear transmutation Nuclear fission Nuclear fusion Uses of isotopes Biological effects of radiation. GCh23-2 Nuclear Reactions Reactions involving changes in nucleus Particle Symbol Mass Charge
of radioactivity and will, therefore, be thoroughly discussed below. Har-nessing these emissions is at the core of nuclear pharmacy, nuclear medicine, and nuclear physics. Radioactivity calculations Nuclear pharmacy and nuclear medicine use many units for quantifying such items such as mass, exposure, dose, and radioactivity. Mass units
Radioactivity and Nuclear Reactions Radioactivity Radioactivity was first discovered in 1896 by Henri Becquerel when a photographic plate wrapped in black paper was exposed when placed in close proximity to a uranium salt. Later, experiments by Marie and Pierre Curie uncovered other radioactive substances and eventually it
Part One: Heir of Ash Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 Chapter 24 Chapter 25 Chapter 26 Chapter 27 Chapter 28 Chapter 29 Chapter 30 .
Section 28.1 – Nuclear Radiation zObjectives: zDiscuss the processes of radioactivity and radioactive decay zCharacterize alpha, beta, and gamma radiation in terms of composition and penetrating power Radioactivity zRadioisotopes – nuclei of isotopes that go through nuclear reactions in an attempt to gain .
CHAPTER 19: RADIOACTIVITY AND NUCLEAR ENERGY INTRODUCTION Most chemical properties depend on the arrangement of electrons, andmany chemical reactions involve the transfer of electrons from one atom to another. But the events and reactions described in this chapter depend on the properties of the nucleus of an atom. The best known
Radioactivity was discovered by Henri Becquerel. Radioactivity refers to the amount of radiation released when an element spontaneously emits energy as a result of the decay of its unstable atoms. The Becquerel is a unit used to measure radioactivity, and stands for 1 disintegration per second. The Curie is a unit of radioactivity equal to 3.7 .
TO KILL A MOCKINGBIRD. Contents Dedication Epigraph Part One Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Part Two Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18. Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 Chapter 24 Chapter 25 Chapter 26
