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Atoms & Isotopes

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.

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Atoms & Isotopes

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  1. Atoms & Isotopes Mrs. Page Chemistry10 Parts of presentation modified from a PowerPoint presentation prepared by J. Crelling, Southern Illinois University

  2. You 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 mass • You 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. Learning Objectives

  3. Contain protons, neutrons, and electrons • Protons & neutrons are found in the nucleus • The nucleus contains most of the mass of an atom • Electrons 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 http://www.universetoday.com/ ATOMS

  4. First subatomic particle discovered • 1897 J.J. Thomson used the cathode ray tube to discover the electron • Has a negative charge (-1) • Mass = 9.110 x 10-28g (0.0005 amu) • Electrons are located in energy levels which make up the electron cloud • Electrons in the outermost energy level are called valence electrons • Valence electrons are responsible the for the reactivity of an atom. ELECTRONS

  5. Observed 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) PROTON

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

  7. Atoms 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) • Isotopesare atoms of the same element having different number of neutrons ISOTOPES

  8. Every element has naturally occurring isotopes • Hydrogen has 3 naturally occurring isotopes • Protium is the most abundant isotope of hydrogen (99.985%) has 1 proton, 0 neutrons, and 1 electron • Deuterium (0.015%) has 1 proton, 1 neutron, and 1 electron • Tritium (0.0001% ?) has 1 proton, 2 neutrons, and 1 electron Naturally Occurring Isotopes

  9. 35Cl 37Cl 1717 chlorine - 35 chlorine - 37 Isotope Example

  10. 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 _______ _______ _______ Isotopes of Carbon

  11. 12C 13C 14C 6 6 6 #P __6____ 6___ ___6___ #N __6___ __7___ ___8___ #E __6____ 6___ ___6___ Solution

  12. An atom of zinc has a mass number of 65. A. Number of protons in the zinc atom B. Number of neutrons in the zinc atom C. What is the mass number of a zinc isotope with 37 neutrons? Zinc problem

  13. Listed on the periodic table • Gives 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 Na 22.99 Atomic Mass

  14. Percent(%) abundance of isotopes • Mass of each isotope of that element • Weighted average = mass isotope1(%) + mass isotope2(%) + … 100 100 Calculating Atomic Mass

  15. Isotopes Mass of Isotope Abundance 24Mg = 24.0 amu 78.70% 25Mg = 25.0 amu 10.13% 26Mg = 26.0 amu 11.17% Atomic Mass of Magnesium (24)(.787) + (25)(.1013) + 26(.1117) = 18.888 + 2.5325 + 2.9042 = 24.3 amu

  16. Two Categories • Unstable – 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 ISOTOPES

  17. Carbon 14 Dating (Geologic Time) • When the organism dies it stops taking in 14C which disappears as it decays to 14N • Americum-241 Used in smoke detectors • Cesuim-137 Used to treat cancerous tumors • Californium-252 Used to inspect luggage for explosives • Cobalt-60 Used to sterilize surgical equipment • Iodine-123 Used to treat thyroid disorders • Plutonium-238 Used to power NASA spaceships USES OF RADIOISOTOPES

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