Nuclear Symbols Mass number p no Atomic number
Nuclear Symbols Mass number (p+ + no) Atomic number (number of p+) Element symbol
RADIOACTIVITY • Nuclei of unstable isotopes called radioisotopes gain stability by undergoing changes • These changes are always accompanied by large amounts of energy • Discovery of radioactivity dealt a blow to Dalton’s theory that atoms are indivisible
RADIATION • Several types of radiation can be emitted during radioactive decay----3 main types • Alpha radiation • Beta radiation • Gamma radiation
Types of Radioactive Decay v alpha production (a): helium nucleus • • 0 v beta production (b): - 1 e 4 2 He
Alpha Radiation Limited to VERY large nucleii.
Beta Radiation
Types of Radioactive Decay vgamma ray production (g): • v 0 vpositron production 1 e : • velectron capture: (inner-orbital electron is captured by the nucleus)
Types of Radiation
Deflection of Decay Particles attract Opposite charges_____ each other. repel Like charges_____ each other.
Nuclear Stability Decay will occur in such a way as to return a nucleus to the band (line) of stability.
Half-life Concept
Sample Half-Lives
Energy and Mass Nuclear changes occur with small but measurable losses of mass. The lost mass is called the mass defect, and is converted to energy according to Einstein’s equation: DE = Dmc 2 Dm = mass defect DE = change in energy c = speed of light Because c 2 is so large, even small amounts of mass are converted to enormous amount of energy.
Nuclear Fission and Fusion • Fusion: Combining two light nuclei to form a heavier, more stable nucleus. • Fission: Splitting a heavy nucleus into two nuclei with smaller mass numbers.
Fission
Fission Processes A self-sustaining fission process is called a chain reaction.
Fusion
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