Model of the atom

• What does atomic theory propose about matter?

  Everything is made of tiny, indivisible particles
• Who originally proposed atomic theory?

  Democritus
• What did John Dalton describe atoms as?

  Solid spheres
• What did Dalton suggest about different types of spheres?

  They make up different elements
• What model did J.J. Thompson propose in 1897?

  The plum pudding model
• What did Thompson's experiments reveal about atoms?

  Atoms contain negatively charged particles
• How did Rutherford's experiments challenge Thompson's model?

  Alpha particles were deflected, proving it wrong
• What did Rutherford propose after his experiments?

  The nuclear model of the atom
• What did Rutherford suggest about the nucleus?

  It contains all the positive charge
• What was the flaw in Rutherford's model?

  No explanation for electron stability around the nucleus
• Who proposed a solution to the flaw in Rutherford's model?

  Niels Bohr
• How did Bohr describe electron movement?

  Electrons orbit the nucleus in shells
• Why is Bohr's model important?

  It prevents the atom from collapsing
• What did Rutherford discover about the nucleus later on?

  It contains protons
• Who provided evidence for neutral particles in the nucleus?

  James Chadwick
• What are neutral particles in the nucleus called?

  Neutrons
• What are the key developments in atomic theory from Democritus to Chadwick?

  • Democritus: Proposed atomic theory (500 BC)
  • Dalton: Described atoms as solid spheres
  • Thompson: Plum pudding model (1897)
  • Rutherford: Nuclear model (deflected alpha particles)
  • Bohr: Electrons orbit nucleus in shells
  • Chadwick: Discovered neutrons in nucleus
• What is the current understanding of the atom's structure?

  Similar to Bohr's model with minor changes
• What is the significance of the empty space in atomic theory?

  Particles are separated by empty space