Chapter 25 – Nuclear Changes 25.1 - Radioactivity.

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  • Chapter 25 Nuclear Changes25.1 - Radioactivity

  • ObjectivesDescribe the structure of an atom and its nucleus.Explain what radioactivity is.Compare and contrast properties of radioactive and stable nuclei.Discuss the discovery of radioactivity.

  • NucleusComposed of protons and neutrons which account for most of the atoms mass

  • Strong forceCauses protons and neutrons to be attracted to each other in the nucleus

  • Video clipThe strong force is powerful only when neutrons and protons are close to each otherThe protons and neutrons in a large nucleus are held less tightly by the strong force than those in a small nucleus

  • RadioactivityThe nuclear decay that occurs when the strong force is not large enough to hold the nucleus together and the nucleus gives off matter and energy

  • IsotopesAtoms of the same element with varying number of neutrons

  • A nucleus with too many or too few neutrons compared to protons is radioactiveAtomic number = number of protons in an atomMass number = number of protons and neutrons in a nucleusIf an element has a neutron to proton ratio of 1.2 or higher than the element is radioactive

  • SymbolAtomic NumberNumber of protonsMass NumberNumber of Neutrons1H11110235U929292235235-92 = 143

  • Element RadioactivityUranium was discovered in 1896 by Henri Becquerel as a radioactive element

    Polonium and Radium were discovered as radioactivity by Marie and Pierre Curie in 1898Video Clip

  • In-Class Assignment/Homework25.1 Reinforcement WKTTomorrow 25.1 Enrichment WKT25.1 & 25.2 Directed Reading WKT

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