CA StandardsStudents know the three most common formsof radioactive decay (alpha, beta, and gamma)and know how the nucleus changes in each typeof decay.Students know alpha, beta, and gammaradiation produce different amounts and kindsof damage in matter and have differentpenetrations.Students know some naturally occurringisotopes of elements are radioactive, as areisotopes formed in nuclear reactions.
Nuclear SymbolsMass number Element (p+ + no) symbol 235 U 92 Atomic number (number of p+)
Types of Radioactive Decayalpha production (a, He): helium nucleus 238 92 U He 4 2 234 90 Thbeta production (b, e): 234 90 Th 234 91 Pa e 0 1 gamma ray production (g): U He 238 92 4 2 Th 2 g 234 90 0 0
Nuclear StabilityDecay will occur insuch a way as toreturn a nucleus tothe band (line) ofstability.
Alpha RadiationAlpha decay islimited to VERYlarge, nucleisuch as those inheavy metals.
Beta RadiationBeta decayconverts aneutron into aproton.
Alpha Particle Beta Particle Gamma Ray Emission Emission Emission 4 Symbol 2 He 2 or 2 a 2 4 0 1 e 0 or 1 b 0 0 g Mass Heavy Light No MassHow it changes Decreases the Converts a No change to the the nucleus mass number neutron into a nucleus by 4 proton Decreases the Increases atomic number atomic number by 2 by 1 Penetration Low Medium High Protection Skin Paper, clothing Lead provided by… Danger Low Medium High
CA StandardsStudents know protons and neutrons in thenucleus are held together by nuclear forcesthat overcome the electromagnetic repulsionbetween the protons.Students know the energy release per gram ofmaterial is much larger in nuclear fusion orfission reactions than in chemical reactions.The change in mass (calculated by E = mc2) issmall but significant in nuclear reactions.
FissionFission - Splitting aheavy nucleus into twonuclei with smaller massnumbers.
Deuterium – Tritium Fusion ReactionFusion - Combining two light nuclei toform a heavier, more stable nucleus.
Energy and MassNuclear changes occur with small but measurablelosses of mass. The lost mass is called the massdefect, and is converted to energy according toEinstein’s equation: DE = Dmc2 Dm = mass defect DE = change in energy c = speed of lightBecause c2 is so large, even small amounts ofmass are converted to enormous amount ofenergy.