Chapter 7

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Chapter 7 The Nucleus

• Atom Discoveries
• A. John Dalton
• -experimented with masses
• volumes of gases
• -found no change in either in
• chemical reactions that atoms react in whole
  ratios
• Billiard Ball Model said atom was solid,
  indivisible, with no parts

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• B. J.J.Thomson
• -used cathode ray tube
• -found metal plates release streams of negative
  particles (electrons)
• Plum Pudding Model said atom was positive
  material with electrons embedded in it
• Electrons have 1- charge
• -have almost no mass
• -can leave atoms

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• C. Ernest Rutherford
• gold foil experiment
• Discovered the nucleus (Nuclear Model)

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• Protons have 1 charge
• -have mass 1 amu
• - never changes
• Isotopes atoms of the same element
• (so same protons)
• with different neutrons
• (so different mass)
• Neutrons have no charge
• -have mass 1 amu

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• II. Nucleus Structure
• A. Atomic protons
• used to identify elements
• elements are in this order on periodic table
• B. Mass protons neutrons
• Atomic mass on periodic table is
• average mass for all isotopes of an element
• C. Oxidation (charge) protons - electrons

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• III. Nuclear Reactions
• Protons Neutrons are made of smaller particles
  called quarks, which can recombine to form other
  particles.
• When these leave nucleus (at the speed of light)
  this is radioactivity high doses can cause
  tissue damage, leukemia, birth defects

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• Types of Particles
• alpha particles He
• beta particles e
• gamma particles
• positron e
• proton H
• neutron n

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• B. Nuclear Fission
• Splits larger element into smaller one
• Can be radioactive decay or bombardment
• Used in
• Nuclear power plants Nuclear medicine
• C. Nuclear Fusion
• Joins together smaller elements /or particles
  to make larger element
• Used in
• Sun Stars, Atom bomb,
• Forming synthetic elements

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• Sample Nuclear Equations
• Write the reaction for an alpha decay of
  Uranium-232. Is this fusion or fission?

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• 2. Write the equation for a beta capture of
  Bromine-80. Is this fusion or fission?

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• 3. Mendeleevium-258 is bombarded with neutrons to
  produce Einsteinium-255 and one other particle.
  What is the other particle? Is this fusion or
  fission?

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• D. Half-Life time for onl-half of radioactive
• sample to decay.
• Amount doesnt matter, time is always the same.
• Examples
• 1. The half-life of Sodium-24 is 15 hours. How
  long does it take to 1/8 of the original amount
  to remain?

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• 2. After 10 years, 75 g of a 100 g sample has
  decayed. What is the half-life of the isotope?
• 3. A 1 kg sample of Radium has a half-life of
  1600 years. How much will remain in
• 4800 years.

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• Quiz Next Week
• Dalton Thomson
• -describe their experiments
• -give the name of their atom models
• -tell what they discovered about the atom
• Rutherford
• -describe the 3 results of his gold foil
  experiment what each told him about the atom
• Tell how to calculate
• Atomic
• Mass
• Oxidation