developing ideas of the atom

• Who proposed the solid sphere model of the atom?

  John Dalton
• What did Dalton's solid sphere model suggest about atoms?

  Atoms are indivisible, solid spheres
• How did Dalton differentiate between elements in his model?

  Different elements have different types of spheres
• What was J.J. Thomson's contribution to atomic theory?

  • Discovered the electron
  • Proposed the plum pudding model
  • Atoms are divisible
• How did Thomson's plum pudding model depict atoms?

  Atoms as spheres of positive charge with electrons
• What year did Rutherford conduct his gold foil experiment?

  1909
• What was the main purpose of Rutherford's gold foil experiment?

  To redefine atomic theory
• What unexpected result did Rutherford observe in his experiment?

  Most alpha particles passed through undeflected
• What did Rutherford conclude about the structure of the atom?

  Atoms are mostly empty space with a nucleus
• What did Rutherford identify as the cause of alpha particle deflection?

  A tiny, dense, positively charged nucleus
• How did Rutherford explain the neutrality of the atom?

  Negative electrons orbit a positive nucleus
• What did Henry Moseley's research reveal about atomic structure?

  • Nuclear charge increases by one unit per element
  • Led to the identification of protons
• What did Rutherford name the positively charged particles in the nucleus?

  Protons
• What mystery did Rutherford speculate about regarding atomic nuclei?

  Why nuclei were heavier than expected
• Who discovered the neutron?

  James Chadwick
• What did the discovery of the neutron explain?

  The mass discrepancy in atomic nuclei
• What was a major flaw in Rutherford's model of the atom?

  • Unable to explain electron stability
  • Electrons should collapse into the nucleus
• What did Niels Bohr propose to address Rutherford's model flaw?

  Electrons orbit in specific energy levels
• How can electrons move between energy levels in Bohr's model?

  By absorbing or emitting light
• What did Bohr's model help explain about atoms?

  • Observed spectra of light
  • Emission and absorption of light
• How did the Bohr model get refined with subshells?

  • Electrons in the same shell have different energy levels
  • Introduced the concept of subshells
• Why is the refined Bohr model still useful today?

  It explains trends in bonding and ionization energy