the nuclear model

• How was the nuclear model modified?


  By the discoveries of electron energy levels, protons, and neutrons
• What was the early model of atomic structure called?

  The Plum Pudding model
• What led to the replacement of the Plum Pudding model?

  The results of the alpha scattering experiment
• What does the nuclear model state about the structure of an atom?


  Most of an atom is empty space with a positive nucleus and negative electrons
• Who proposed that electrons orbit the nucleus at specific distances?


  Neils Bohr
• What are the specific distances where electrons orbit the nucleus called?


  Energy levels or shells
• What are protons?

  Tiny positive particles in the nucleus
• How many protons does a hydrogen atom have?

  One proton
• How many protons does a helium atom have?

  Two protons
• What determines the amount of positive charge in the nucleus?

  The number of protons
• Who discovered neutrons?

  James Chadwick
• What is the radius of an atom approximately?

  0.1 nanometers or $1 \times 10^{-10} \text{ m}$
• What is the radius of the nucleus approximately?


  $1 \times 10^{-14} \text{ m}$
• How does the radius of the nucleus compare to the radius of the atom?

  The radius of the nucleus is less than 1/10,000 of the radius of the atom
• Where is most of the mass of the atom found?

  In the nucleus
• What is the relative charge of protons?


  Positive one
• What is the relative charge of neutrons?


  Zero
• What is the relative charge of electrons?


  Negative one
• Why do atoms have no overall charge?


  Because the number of electrons equals the number of protons
• What cancels out the positive charges in an atom?

  The negative charges on the electrons
• What is the relative mass of protons and neutrons?


  One
• How does the relative mass of electrons compare to protons and neutrons?

  Electrons have a much smaller relative mass
• What are the relative charges and masses of protons, neutrons, and electrons?

  • Protons:
  • Relative charge: +1
  • Relative mass: 1
  • Neutrons:
  • Relative charge: 0
  • Relative mass: 1
  • Electrons:
  • Relative charge: -1
  • Relative mass: very small
• What is the final version of the nuclear model of atomic structure?


  • Contains a positive nucleus
  • Nucleus has protons and neutrons
  • Electrons orbit the nucleus at specific energy levels
  • Most of the atom is empty space