The nuclear model

• What should you be able to describe by the end of the video?

  The nuclear model of atomic structure and its modifications
• 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
• What did Neils Bohr propose about electrons?

  Electrons orbit the nucleus at specific distances
• What are the specific distances where electrons orbit 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 do neutrons contribute to the nucleus?

  They are neutral particles
• What is the approximate radius of an atom?

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

  $1 \times 10^{-14} \text{ m}$
• 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
• 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 charges in an atom?

  The positive charges on protons are cancelled by the negative charges on 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 than protons and neutrons
• Do you need to know the exact relative mass of an electron?

  No, just that it is very small
• 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
• What are the key facts about atomic structure that are often tested in exams?

  • The Plum Pudding model was replaced by the nuclear model
  • The nucleus contains protons and neutrons
  • Electrons have specific energy levels
  • Atoms have no overall charge