The Nuclear Model

• How was the nuclear model modified?

  By 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 most of an atom?

  It is simply empty space
• What is found in the center of an atom according to the nuclear model?

  A positive nucleus containing most of the mass
• Where are electrons located in the nuclear model?

  At the edge of the atom
• Who proposed that electrons orbit the nucleus at specific distances?

  Neils Bohr
• 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 are neutrons?

  Neutral particles in the nucleus
• What is the approximate radius of an atom?

  0.1 nanometers
• How is the radius of an atom expressed in meters?

  As $1 \times 10^{-10} \text{ m}$
• 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?

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

  In the nucleus
• What is relative charge?

  The charge of one particle compared to another
• 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 protons
• What cancels the positive charges in an atom?

  The negative charges on the electrons
• What is relative mass?

  The mass of one particle compared to another
• What is the relative mass of protons and neutrons?

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

  It is much smaller
• Do you need to know the exact relative mass of an electron?

  No, just that it is very small
• What are the key components of the nuclear model of atomic structure?

  • Positive nucleus at the center
  • Electrons orbiting at specific energy levels
  • Protons and neutrons in the nucleus
  • Most of the atom is empty space
• 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