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# Chap. 21: Radioactivity & Nuclear Chemistry ## Radioactivity - Emission of subatomic particles at high energy by nuclei (radioactive) ### Isotope notation - Isotope is called nuclide - $ \symbol{x} $ → element - Same element, different # of neutrons - mass# → $ A $ - atomic# → $ Z $ - 1P : p...

# Chap. 21: Radioactivity & Nuclear Chemistry ## Radioactivity - Emission of subatomic particles at high energy by nuclei (radioactive) ### Isotope notation - Isotope is called nuclide - $ \symbol{x} $ → element - Same element, different # of neutrons - mass# → $ A $ - atomic# → $ Z $ - 1P : proton - 1n : neutron - 0e : electron - 4 2α or $^{4}_{2}He$ : alpha - $ ^{0}_{-1}β $ or $ ^{0}_{+1}β $ : beta or positron ## N/Z ratio - Green dots: stable nuclei - Yellow: unstable nuclei - Z = 1-20 Stable N/Z ≈ 1 - Z = 20-40 stable N/Z → 1.25 - Z = 40-80 Stable N/Z → 1.5 - Above Z = 83 unstable (radioactive) - N/Z is high: n → p by beta emission - N/Z is low: p → n by positron emission or e-capture ## Magic numbers for nucleons - Nor Z = 2, 8, 20, 28, 50, 82, N=126 ## Nuclear fission - Splitting of the nucleus, releases lots of energy - Small nuclide are accelerated & put together=big nuclide ## Critical mass - Amount of isotope needed to produce a fission reaction. ## Nuclear Fusion - Small nuclide put together ## Energy from fission $ E = mc^{2} $ 3.00 × 108 ## Mass defect - Difference in mass between nucleus & sum of separated particles making up nucleus ## Nuclear Binding Energy - Energy released when nucleus forms - The greater the more stable ## Radioactive Rays - Radioactive rays → air becomes ionized ## All radioactive decay - All radioactive decay is first order ## Rate Rate = k N N = # of nuclei k = rate constant ## Half-Life - Time it takes for 1/2 of parent nuclide to decay $ t^{1/2} = \frac{0.693}{k} $ ## Integrated Rate Law - $ ln(N_{t}/N_{0}) = -kt $ - $ N_{t} $ = # of nuclei at time t - $ N_{0} $ = Initial #nuclei ## 1MeV - 1MeV = 1.602 × 10-13 J ## 1 amu of mass defect - 1 amu of mass defect = 931.5 MeV ## Mass Defect formula mass defect = Mnucleus - Mparticles Mnucleus = Matom - Me-inatom ## Transmutation - Transformation of one element to another by nuclear ## Alpha decay - Unstable nuclei emits alpha particle (2p & 2n) - Highest ionizing power & low penetrating power ## Beta decay - Unstable nuclei emits e- - 10 times for penetrating paver & lower ionizing power ## Gamma emission - High energy radiation - Least ionizing power & highest penetrating power ## Positron emission - Unstable nucleus emits a positron - proton → neutron & emits positron ## Electron Capture - Inner orbital e⁻ is absorbed by nucleus - Proton is converted into neutron ## Nucleons - Particles in nucleus held together by strong force ## Linear accelerator - Particle accelerator (tube shaped) ## Cyclotron - Charge particle is accelerated in ring shape