1.3.3 The development of the neutron model

• What is the name of the positively charged matter shown in the image?

  Positively charged matter
• What experiment later disproved the plum pudding model?

  Rutherford's gold foil experiment
• Where is the positive charge concentrated in an atom according to Rutherford's findings?

  In a small nucleus at the center
• Who proposed the plum pudding model of the atom?

  J.J. Thomson
• What is the purpose of the thin gold foil shown in the image?

  • The thin gold foil is used to allow the α-particles to pass through and be detected by the device.
• What did the results of Rutherford's experiment show about most alpha particles?

  Most passed through unaffected
• How does the plum pudding model visualize the arrangement of electrons?

  Scattered throughout like plums in pudding
• What was the significance of the plum pudding model?

  First atomic model based on experimental evidence
• What are the three fundamental subatomic particles?

  Protons, neutrons, electrons
• How did Rutherford's gold foil experiment challenge the plum pudding model?

  It showed that atoms have a dense nucleus
• What does the plum pudding model depict atoms as?

  A sphere of uniform positive charge
• What type of particles did Rutherford fire at gold foil?

  Alpha particles
• What fundamental change did the discovery of neutrons bring to atomic structure understanding?

  It changed our understanding of atomic structure
• What material was used to detect the protons released in Chadwick's experiment?

  Paraffin wax
• How did Rutherford's findings challenge Thomson's model of the atom?

  It showed most space is empty
• Why do protons repel each other in the nucleus?

  Because they are both positively charged
• What was the outcome for a few alpha particles in Rutherford's experiment?

  A few bounced back
• What happens to nuclei without neutrons?

  They would be unstable and elements couldn't exist
• What is the purpose of the vacuum pump shown in the image?

  To vacuum pump
• What are the small spheres in the image?

  Electrons
• What did Rutherford's experiment reveal about electron positions?

  Electrons orbit the nucleus
• What are protons?

  Positively charged particles in the nucleus
• How do the relative charges and locations of protons, neutrons, and electrons determine the overall charge and stability of an atom?

  • The number of protons and electrons determines the overall charge of the atom
  • The number of neutrons affects the stability of the nucleus
  • Atoms are electrically neutral when the number of protons equals the number of electrons
• What defines isotopes of an element?

  Different numbers of neutrons, same protons
• What are the atomic numbers of the carbon isotopes shown in the image?

  • Carbon 12: Atomic number 6
  • Carbon 14: Atomic number 6
• How does the device shown in the image work?

  1. Po source emits alpha particles (α's)
  2. Alpha particles interact with unknown radiation
  3. Protons are produced from the interaction
  4. Protons are detected by the amplifier and oscillograph
• In the plum pudding model, what are the negatively charged particles called?

  Electrons
• How are isotopes represented in atomic notation?

  Using mass number and atomic number
• How did Rutherford's experiment change our understanding of atomic structure?

  • Disproved Thomson's model
  • Introduced the concept of a nucleus
  • Established that atoms are mostly empty space
  • Changed the view of electron arrangement
• What are the key facts about protons?

  • Charge: +1
  • Location: Nucleus
  • Mass: ~1 atomic mass unit (amu)
• What is the role of neutrons in the nucleus?

  They provide strong nuclear force to hold protons
• Where are protons located in an atom?

  In the atomic nucleus
• What did Rutherford's gold foil experiment demonstrate about protons?

  Positive charge is concentrated in the nucleus
• What happened to some alpha particles during the experiment?

  Some were slightly deflected
• How are the electrons arranged in the image?

  • The electrons are arranged in a spherical pattern around the positively charged matter
  • The electrons are evenly distributed around the positively charged matter
• What is the purpose of the electrons in the image?

  To show that the matter is positively charged
• What is the atomic notation for carbon-12?

  ${}^{12}_{6}C$
• What is the purpose of the protons shown in the image?

  To be detected by the amplifier and oscillograph
• What are the key reasons for the need for neutrons in atomic structure?

  • Protons repel each other due to positive charge
  • Neutrons provide strong nuclear force
  • Neutrons stabilize the nucleus, allowing elements to exist
• What were the key findings of Chadwick's neutron discovery?

  • Neutral particles with neutron mass were produced
  • These particles penetrated matter more deeply than protons
  • They could eject protons from hydrogen-containing materials