1.3.1 Historical models: Dalton, Thomson, Rutherford, Bohr

• What are the negatively charged particles in an atom called?

  Electrons
• Why was Dalton's atomic model considered revolutionary?

  It showed matter is made of separate particles
• What type of particle is represented by the gray spheres in the image?

  Neutron
• How do atoms behave according to Dalton's atomic model?

  Atoms join but never disappear
• What type of particle is represented by the blue spheres in the image?

  Electron
• What is the name given to the positively charged matter in the image?

  Positively charged matter
• What are the key components of the Bohr atomic model?

  • Nucleus with protons and neutrons
  • Electrons orbiting the nucleus in discrete energy levels
  • Electrons can only occupy certain allowed energy levels
  • Electrons can jump between energy levels by absorbing or emitting photons
• What is the total mass of the water molecule shown?

  18 mass units
• What is the nucleus?

  A tiny, dense center of the atom
• Who proposed the atomic model that describes matter as indivisible spheres?

  Dalton
• How does the Bohr model differ from the modern quantum mechanical model of the atom?

  • Bohr model depicts electrons in circular orbits, while quantum model describes electrons in probabilistic wave functions
  • Bohr model has discrete energy levels, while quantum model has a continuous range of energy levels
  • Bohr model is a simplified classical model, while quantum model is based on quantum mechanics
• What does the image suggest about the stability of an atom?

  • The attraction between the electrons and positively charged matter holds the atom together
  • This arrangement suggests the atom is stable
  • Any disruption to this balance could make the atom unstable
• What type of particle is represented by the green and orange spheres in the image?

  Proton
• What are the key features of Dalton's Atomic Model?

  • Matter is made of tiny indivisible spheres
  • Matter is discrete, not continuous
  • Confirms conservation of mass
  • Atoms join but do not disappear
• What led to the rejection of Thomson's Plum Pudding Model?

  The discovery of the nucleus showed it was incorrect
• How does the water molecule form according to Dalton's Atomic Theory?

  • 1 oxygen atom (16 mass units)
  • 2 hydrogen atoms (2 mass units each)
  • Total mass of water molecule = 18 mass units
• What were the key findings from Rutherford's gold foil experiment?

  1. Most particles passed through - atom mostly empty space
  2. Some particles deflected slightly - indicating positive charges
  3. Very few particles bounced back - suggesting a dense core
• What is the name of the device shown in the image?

  Detector
• What is the name of the theory shown in the image?

  Dalton's Atomic Theory
• How did Rutherford's experiment impact our understanding of atomic structure?

  It revolutionized our understanding of atomic structure
• What is the name of the particle shown flowing through the device?

  α-particle
• What does it mean when particles deflect slightly in Rutherford's experiment?

  They are bouncing off positive charges
• How does the lead block in the device function?

  • The lead block shields the detector from external radiation
  • This allows the detector to focus on measuring the α-particles from the radium source
• What is the significance of each shell in the Bohr model?

  Each shell holds a certain number of electrons
• How are electrons distributed in Thomson's model?

  Evenly distributed like plums in pudding
• What did the results of Rutherford's experiment indicate about the atom's structure?

  Atoms are mostly empty space
• What are the key components of Dalton's Atomic Theory?

  • All matter is made up of tiny indivisible particles called atoms
  • Atoms of the same element are identical, while atoms of different elements have different properties
  • Atoms cannot be created, divided, or destroyed
  • Atoms combine in simple whole-number ratios to form compounds
• What principle did Dalton's work confirm regarding atoms?

  The principle of conservation of mass
• What is the relationship between electrons and positively charged matter in the image?

  • Electrons are negatively charged particles
  • Positively charged matter is attracted to the electrons
  • This attraction holds the atom together
• What is the purpose of the thin gold foil in the device?

  • The thin gold foil is used to detect the flow of α-particles
  • It allows the α-particles to pass through and be detected
• What did Rutherford use in his experiment?

  Alpha particles and thin gold foil
• What are the key features of the Bohr model of the atom?

  • Electrons orbit the nucleus
  • Fixed energy levels or electron shells
  • Shells are like staircase steps
  • Each shell holds a specific number of electrons
• What was a significant limitation of Thomson's Plum Pudding Model?

  It did not account for the nucleus
• What is the name of the atomic model shown in the image?

  Bohr atomic model
• How does the arrangement of electrons and positively charged matter in the image represent the structure of an atom?

  • The positively charged matter represents the nucleus of the atom
  • The electrons are arranged around the nucleus
  • This arrangement shows the basic structure of an atom
• What does Dalton's atomic model suggest about matter?

  It is made of tiny indivisible spheres
• What does the Bohr model show about electrons?

  Electrons orbit the nucleus at fixed energy levels
• What does Thomson's Plum Pudding Model describe the atom as?

  A positive sphere with negative electrons
• What is the name of the radioactive material shown in the image?

  Radium
• Why was Thomson's model considered an improvement over Dalton's model?

  It included subatomic particles in the atom