The history of the atom

• What is the main topic of the video discussed in the study material?

  The history of the atom
• What does atomic theory propose about matter?

  Everything is made up of tiny particles that cannot be broken down further
• Who originally proposed the atomic theory?

  Democritus
• When did Democritus live?

  Around 500 BC
• How long did it take for anyone to improve on Democritus's ideas?

  About 2300 years, until the 1800s
• What did John Dalton describe atoms as?

  Solid spheres
• What was Dalton's important suggestion regarding different elements?

  Different types of spheres might 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 cannot be solid spheres and contain negatively charged particles
• What are the negatively charged particles in atoms called?

  Electrons
• What did Rutherford's experiments with alpha particles demonstrate?

  Some alpha particles were deflected, proving Thompson's theory wrong
• What did Rutherford propose after his experiments?

  The nuclear model, with a compact nucleus containing all positive charge
• What was the flaw in Rutherford's nuclear model?

  There was nothing stopping the electrons from collapsing into the nucleus
• Who suggested that electrons orbit the nucleus in 1913?

  Niels Bohr
• How did Bohr's model prevent the atom from collapsing?

  Electrons orbit the nucleus in shells
• What did further experiments by Rutherford reveal about the nucleus?

  The positive charge in the nucleus is made up of protons
• Who provided evidence for neutral particles in the nucleus?

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

  Neutrons
• What are the key developments in the history of atomic theory?

  • Democritus proposed atomic theory (500 BC)
  • John Dalton described atoms as solid spheres (1800s)
  • J.J. Thompson introduced the plum pudding model (1897)
  • Ernest Rutherford proposed the nuclear model (1909)
  • Niels Bohr suggested electrons orbit the nucleus in shells (1913)
  • Discovery of protons and neutrons in the nucleus
• How did the understanding of the atom evolve through different scientists' contributions?

  • Democritus: Atoms as indivisible particles
  • Dalton: Solid spheres representing elements
  • Thompson: Atoms contain electrons (plum pudding model)
  • Rutherford: Nucleus with positive charge
  • Bohr: Electrons in orbits prevent collapse
  • Chadwick: Discovery of neutrons