Atomic and Electronic Structure

• What were atoms described as in the early 1800s?

  Solid spheres that can't be divided
• What does the plum pudding model represent?

  A ball of positive charge with electrons
• In what year was the nuclear model proposed?

  1909
• What is the main feature of the nuclear model?

  Mass is concentrated in a positive nucleus
• What experiment demonstrated the nuclear model?

  Firing α-particles at gold foil
• What was observed when α-particles were fired at gold foil?

  Most particles passed through, some deflected
• What year was the Bohr model introduced?

  1913
• How do electrons behave in the Bohr model?

  They orbit the nucleus in fixed shells
• Who provided evidence for neutrons in 1932?

  James Chadwick
• What charge do neutrons have?

  They are neutral particles
• What particles are found in the nucleus?

  Protons and neutrons
• What gives the nucleus its positive charge?

  Protons in the nucleus
• How do electrons occupy shells in an atom?

  • Electrons fill each shell before a new one
  • Start with the lowest energy shell
  • Lowest energy shells are closest to the nucleus
• What is the maximum number of electrons allowed in each shell?

  • Shell 1: 2 electrons
  • Shell 2: 8 electrons
  • Shell 3: 8 electrons
• How can electronic structure be represented?

  As numbers, like 2, 8, 1
• Do students need to remember specific dates in atomic history?

  No, specific dates are not required