1.3.1 Historical models: Dalton, Thomson, Rutherford, Bohr

• What limitation did Thomson's model have according to later experiments?

  It didn't explain the atom's structure correctly
• What is the purpose of the lead block shown in the image?

  • The lead block is used to emit the α-particles that are detected by the device.
• What is Dalton's Atomic Theory primarily about?

  It describes the nature of atoms
• What is Thomson's model of the atom called?

  Plum pudding model
• What does Dalton's Atomic Theory state about atoms of the same element?

  All atoms of the same element are identical
• What is the purpose of the electrons in the image?

  To show that the matter is positively charged
• What are the small spheres in the image?

  Electrons
• If all gold atoms are the same, what can we infer about other elements?

  All atoms of each element are identical
• What model did Bohr build upon?

  Rutherford's model
• What are the key points of Dalton's Atomic Theory?

  • Everything is made of atoms
  • Atoms are tiny particles
  • All atoms of the same element are identical
• What is the name of the device shown in the image?

  Detector
• How does Thomson's plum pudding model describe the atom?

  As a positive sphere with scattered electrons
• If the radius of the sphere in the image is 5 cm, what is the area of the sphere?

  $4\pi (5)^2 \text{ cm}^2 =$$100\pi \text{ cm}^2$
• What are the key features of Thomson's plum pudding model?

  • Atoms are positive spheres
  • Negative electrons are scattered throughout
  • Improved upon Dalton's model
• What is the name of the particle shown flowing through the device?

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

  Positively charged matter
• 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 Rutherford fire through gold foil in his experiments?

  Alpha particles
• What happens when electrons gain or lose energy in Bohr's model?

  They can jump between energy levels
• What are the different energy levels shown in the image?

  • I Energy Level
  • II Energy Level
  • III Energy Level
  • IV Energy Level
  • Nucleus
• What are the specific capacities of electron shells in Bohr's model?

  • Electrons exist in defined orbits
  • Shells fill sequentially: 2, 8, 18, 32…
  • Electrons can jump between levels with energy changes
• How do the energy levels relate to the electron configuration of an atom?

  • Electrons occupy the different energy levels based on their energy
  • The energy levels represent the allowed energy states for electrons in an atom
  • The number of electrons in each energy level follows a specific pattern
• What is the value of the IV Energy Level?

  32
• What did Rutherford observe when he fired alpha particles?

  Some particles were deflected, others passed through
• What does the deflection of some particles indicate about the atom?

  It has a positive charge
• What improvement did Thomson's model provide over Dalton's model?

  It explained subatomic particles and their charges
• How does the detector in the image work to detect the α-particles?

  • The detector measures the deflection of the α-particles as they pass through the thin gold foil, providing information about their charge and mass.
• What were the key findings of Rutherford's experiments?

  1. Most particles passed straight through, indicating empty space.
  2. Some were deflected slightly by positive charge.
  3. Very few bounced back, indicating a small dense nucleus.
• What orbits around the nucleus in Rutherford's model?

  Electrons
• How does Rutherford's model differ from Thomson's model regarding atomic structure?

  Rutherford's model has a nucleus, Thomson's does not
• What is the relationship between the energy levels shown in the image?

  • The energy levels are arranged in concentric circles around the nucleus
  • The energy levels increase in energy from the innermost (I) to the outermost (IV)
  • Electrons occupy the different energy levels based on their energy
• What are the fixed paths for electrons called in Bohr's model?

  Electron shells
• What does the small dense nucleus contain?

  Positive charge
• What is the value of the I Energy Level?

  2
• What is the value of the II Energy Level?

  8
• What is the value of the III Energy Level?

  18
• How do electrons orbit the nucleus in Bohr's model?

  In fixed energy levels like steps
• 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 model did Rutherford's experiments overturn?

  Thomson's plum pudding model
• If the radius of the circular path of the α-particles is $r$, what is the formula to calculate the centripetal force acting on the α-particle?


  $F_c =$$\frac{mv^2}{r}$