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Notes 39 - Topic 7 - Atomic and Nuclear Physics

Notes 39 - Topic 7 - Atomic and Nuclear Physics - ------------------------------------------------------------------------------------------------ T he Elements h ttp://www.privatehand.com/flash/elements.html 7. 1.5 Define: nuclide, isotope, nucleon 7 .1.6 Nuclear Terminology and Symbols

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Notes 39 - Topic 7 - Atomic and Nuclear Physics

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  1. Notes 39 - Topic 7 - Atomic and Nuclear Physics ------------------------------------------------------------------------------------------------- The Elements http://www.privatehand.com/flash/elements.html 7.1.5 Define: nuclide, isotope, nucleon 7.1.6 Nuclear Terminology and Symbols 7.1.7 Nuclear Interactions - The very existence of isotopes is evidence for the existence of neutrons; - To be isotopes of the same element, the # of protons must be the same, yet there must be a difference in mass; - There is no way to explain the difference in the masses of two isotopes of the same element without the existence of neutrons. • In 1932, James Chadwick discovered the neutron as the result of alpha particle bombardment of beryllium (Be). He was awarded the Nobel Prize in Physics in 1935 for his discovery and added neutrons to protons in the nucleus of the Planetary Model. James Chadwick http://chemcases.com/nuclear/nc-01.htm

  2. •nuclide or isotope - atoms of one element that have the same number of protons but a different number of neutrons; • nucleon - a subatomic particle found in the nucleus of an atom; protons and neutrons are nucleons; • atomic number (Z) - the number of protons in the nucleus of an atom; • mass number or nucleon # - total of all nucleons (protons plus neutrons) found in the nucleus of an atom;

  3. Conventions for Nuclear Symbols A X ... X is the symbol for the element; A is the mass #; Z is the atomic #; Z 1p ... the proton; 1 1 n ... the neutron; 0 0 e ... the electron; -1

  4. Examples 3H ... Tritium (or Hydrogen-3); 1 proton and 2 neutrons in the nucleus; 1 2H ... Deuterium (or Hydrogen-2); 1 proton and 1 neutron in the nucleus; 1 1H ... Hydrogen; only 1 proton in the nucleus (simplest nucleus); 1

  5. 37Cl ... Chlorine-37; 17 protons and 20 neutrons in the nucleus; 17 35Cl ... Chlorine-35; 17 protons and 18 neutrons in the nucleus; 17

  6. Analyzing an Isotope... 17O-2 8 atomic # = ___; mass # = ___; # p’s = ___; # n’s = ___; # e’s = ___

  7. For all events in the universe, there are only 4 different forces responsible: force of gravity... - attractive force between all objects with mass; - weakest of all forces; - range of force is infinite; - magnitude of force is inversely related to square of distance (strength diminishes rapidly with distance); weak nuclear force... - attractive force only between nucleons (p’s and n’s); - stronger than gravitational forces; - range of force limited to diameter of neutrons (eg., 1 x 10-17 m)...it diminishes to zero rapidly after that; - plays a part in the decay of n’s into p’s and e’s;

  8. electromagnetic force... - force of attraction and/or repulsion between charged objects; - weaker only than the strong nuclear force; - range of force is infinite; - magnitude of force is inversely related to square of distance (strength diminishes rapidly with distance); strong nuclear force... - attractive force only between nucleons (p’s and n’s); - strongest of all forces; - range of force limited to distance between nucleons (eg., 1 x 10-15 m)...it diminishes to zero rapidly after that; - nuclei are stable only when a certain ratio of n’s to p’s exists... if too many n’s are present, the nucleus is unstable and undergoes radioactive decay!!

  9. Relative Strengths of Forces Gravity = 1...carried by Gravitons*; Weak Nuclear Force = 1x1032...carried by W+/- and Zo; Electromagnetic Force = 1x1036...carried by Photons; Strong Nuclear Force = 1x1038...carried by Gluons; (*Not identified or found as yet)

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