The history of the atom

• What is the main topic of the video?

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

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

  Democritus
• How long after Democritus' proposal did Dalton improve on atomic theory?

  About 2300 years
• 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 a flaw in Rutherford's nuclear model?

  No explanation for electron stability around the nucleus
• Who proposed that electrons orbit the nucleus?

  Niels Bohr
• How did Bohr's model prevent atomic collapse?

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

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

  James Chadwick
• What is the current understanding of the atom's structure?

  It consists of protons, neutrons, and electrons
• What are the key developments in atomic theory from Democritus to Chadwick?

  • Democritus: Proposed atomic theory
  • Dalton: Described atoms as solid spheres
  • Thompson: Introduced the plum pudding model
  • Rutherford: Proposed the nuclear model
  • Bohr: Suggested electrons orbit in shells
  • Chadwick: Discovered neutrons in the nucleus