Radiology Tutorials: Physics Course - Lecture Notes

Introduction to Atomic Structure

• Atoms are made up of three main particles: protons, neutrons, and electrons.
  • Protons: Positively charged particles.
  • Neutrons: Neutral particles.
  • Electrons: Negatively charged particles that orbit the nucleus.

Rutherford-Bohr Model of the Atom

• Protons and neutrons are packed in the nucleus.
• Electrons orbit the nucleus similar to planets orbiting the sun, held in place by the electromagnetic force.

Electron Energy Shells

• Electrons exist in specific energy shells.
• Energy levels are unique to each element.

Atomic Number and Chemical Symbol

• The number of protons defines an element.
  • In an uncharged atom, the number of electrons equals the number of protons.
• Notation:
  • X = Chemical symbol of the element.
  • Z = Atomic number (number of protons).

Mass Number

• Mass number (A) = Total number of protons + Total number of neutrons.
  • Example: Carbon has 6 protons and 6 neutrons (mass number = 12) - referred to as carbon-12.
• Changing the number of neutrons (while keeping protons the same) results in isotopes.
  • Example: Carbon-13 has 7 neutrons.

Classification of Nuclides

• Nuclides: General term for atoms or elements.
  • Isotopes: Same number of protons, different number of neutrons (e.g., carbon-12 vs. carbon-13).
  • Isobars: Same mass number, different atomic numbers (e.g., molybdenum vs. technetium).
  • Isotones: Same number of neutrons, different atomic numbers (e.g., iodine-131 and xenon-132).
  • Isomers: Same number of protons, neutrons, and electrons, but different energy configurations (e.g., metastable technetium).

Upcoming Topics

• Next lecture will cover deeper insights into energy levels and electron orbitals.
• Further subdivisions of atomic constituents into subatomic particles will lead into quantum physics.