atoms & isotopes

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Atoms & Isotopes. Mrs. Page Chemistry10. Parts of presentation modified from a PowerPoint presentation prepared by J. Crelling, Southern Illinois University. You will be able to define what an isotope is. - PowerPoint PPT Presentation


  • ATOMS & ISOTOPESMrs. PageChemistry10Parts of presentation modified from a PowerPoint presentation prepared by J. Crelling, Southern Illinois University

  • LEARNING OBJECTIVESYou will be able to define what an isotope is.You will be able to determine the number of protons, neutrons, and electrons in different isotopes of the same element.You will understand that atomic massYou will understand what radioactivity is the average of the naturally occurring isotopes of an element.You will be able to give examples of how radioisotopes are used in industry and medicine.

  • ATOMSContain protons, neutrons, and electronsProtons & neutrons are found in the nucleusThe nucleus contains most of the mass of an atomElectrons are distributed around the nucleus in energy levels/shells/orbitals (which make up the electron cloud)The outermost electrons in the shell farthest from the nucleus are called valence electrons

  • ELECTRONSFirst subatomic particle discovered1897 J.J. Thomson used the cathode ray tube to discover the electronHas a negative charge (-1)Mass = 9.110 x 10-28 g (0.0005 amu)Electrons are located in energy levels which make up the electron cloudElectrons in the outermost energy level are called valence electronsValence electrons are responsible the for the reactivity of an atom.

  • PROTONObserved by E. Goldstein in 1896 Rutherford is given credit for showing that atoms contain both negatively and positively charged particles (gold foil experiment)Has a charge of +1 Relative Mass of 1 AMU (1.673 x 10-24 g)

  • NEUTRONThird major subatomic particle discovered (1932 James Chadwick)No charge (neutral)Relative Mass of 1 AMU (1.675 x 10-24 g)

  • ISOTOPESAtoms of the same element have the same atomic number (# of protons) and the same chemical properties.However, atoms of the same element may have different numbers of neutrons (and therefore different atomic mass)Isotopes are atoms of the same element having different number of neutrons

  • NATURALLY OCCURRING ISOTOPESEvery element has naturally occurring isotopesHydrogen has 3 naturally occurring isotopesProtium is the most abundant isotope of hydrogen (99.985%) has 1 proton, 0 neutrons, and 1 electronDeuterium (0.015%) has 1 proton, 1 neutron, and 1 electronTritium (0.0001% ?) has 1 proton, 2 neutrons, and 1 electron

  • ISOTOPE EXAMPLE35Cl37Cl1717 chlorine - 35 chlorine - 37

  • ISOTOPES OF CARBON Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12C 13C 14C 6 6 6 #P _______ _______ _______ #N _______ _______ _______ #E _______ _______ _______


    12C 13C14C 6 6 6#P __6___ _ 6___ ___6___ #N __6___ _ _7___ ___8___ #E __6___ _ 6___ ___6___

  • ZINC PROBLEMAn atom of zinc has a mass number of 65. A.Number of protons in the zinc atom B.Number of neutrons in the zinc atomC. What is the mass number of a zinc isotope with 37 neutrons?

  • ATOMIC MASSListed on the periodic tableGives the mass of average atom of each element compared to 12C Average atom based on all the isotopes and their abundance %Atomic mass is not a whole number mass number is a whole number


  • CALCULATING ATOMIC MASSPercent(%) abundance of isotopesMass of each isotope of that elementWeighted average = mass isotope1(%) + mass isotope2(%) + 100 100

  • ATOMIC MASS OF MAGNESIUM Isotopes Mass of Isotope Abundance 24Mg = 24.0 amu 78.70%

    25Mg = 25.0 amu 10.13%

    26Mg = 26.0 amu 11.17%

    (24)(.787) + (25)(.1013) + 26(.1117) =18.888 + 2.5325 + 2.9042 = 24.3 amu

  • ISOTOPESTwo CategoriesUnstable isotopes that continuously and spontaneously break down/decay in other lower atomic weight isotopes Stable isotopes that do not naturally decay but can exist in natural materials in differing proportions

  • USES OF RADIOISOTOPESCarbon 14 Dating (Geologic Time)When the organism dies it stops taking in 14C which disappears as it decays to 14NAmericum-241 Used in smoke detectorsCesuim-137 Used to treat cancerous tumorsCalifornium-252 Used to inspect luggage for explosivesCobalt-60 Used to sterilize surgical equipmentIodine-123 Used to treat thyroid disordersPlutonium-238 Used to power NASA spaceships



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