Nuclear Chemistry Basics

• Nuclear chemistry is the study of the structure and behavior of matter.
• The atom has a diameter that is 1:100,000 the size of the nucleus.
• Protons and neutrons are found in the nucleus.

Nuclear Science

• Nucleons are protons and neutrons.
• A nuclide is represented by the symbol "X", with "Z" as the subscript (atomic number) and "A" as the superscript (mass number) on the left side.

History of Radioactivity

• French scientist Henery Becquerel discovered radioactivity.
• Uranium atoms are unstable because they emit particles or energy to become more stable.
• These emissions could expose and fog photographic plates
• Marie Curie and her husband discovered polonium and radium, which both emitted uranic rays.
• The name was then changed from "uranic rays" to "radioactivity".

Isotopes

• Isotopes are atoms of the same element that have the same atomic number but different mass numbers.
• Some isotopes are unstable and radioactive.
• Radioactive isotopes are also called radionuclides.
• Radioactive elements are elements in which atoms are unstable and break down to form atoms of other elements.
• This releases radiation in the form of invisible small particles and high-energy waves.
• Examples:
  • Isotopes of hydrogen: Protium, Deuterium, Tritium
  • Isotopes of carbon: Carbon-12, Carbon-13, Carbon-14
  • Isotopes of oxygen: Oxygen-16, Oxygen-17, Oxygen-18

Radiation

• Radiation is energy traveling through space in the form of particles or electromagnetic waves.
• Examples: X-rays, gamma rays, alpha particles, UV light.

Types of Radiation

• Non-ionizing radiation (radio, microwave, infrared, visible light) is low energy and cannot directly alter the chemical structure of material.
• Ionizing radiation has enough energy to remove electrons from atoms, which can cause chemical bonds to break and harm the human body when it penetrates tissues.
• Ionizing radiation cannot be tasted, felt, smelled, or seen.
  • Examples: UV, X-ray, Gamma, Cosmic rays

Radiation Dangers

• Acute radiation damage results from exposure to large amounts of radiation in a short period, which kills many cells and weakens the immune system.
• Ionizing radiation takes electrons from stable compounds in living organisms, leaving highly reactive unpaired electrons (free radicals).
• These free radicals cause reactions in the cells of living organisms, leading to genetic mutations and potentially cancer.

Types of Radioactivity

• Alpha Particles

  • Helium nucleus without electrons (positively charged) with the highest charge.
  • The largest particle emitted by radioactive nuclei.
  • Average energy: 5 MeV
  • Speed: 15*10^6 m/s
  • High relative ionizing ability.
  • Consists of 2 neutrons and 2 protons bound to the nucleus of a Helium atom.
  • Least powerful and most densely ionizing, which can cause mutations in living tissue and lead to cancer.
  • Least dangerous because it can be stopped by skin or a sheet of paper.
  • Uses: Smoke alarms. A tiny amount of Americium-241 (placed between two metal sheets) emits alpha radiation that knocks electrons off atoms in the air, ionizing oxygen and nitrogen atoms. The charged oxygen and nitrogen atoms are attracted to a negative plate, while the electrons are attracted to a positive plate, generating a small continuous current. When smoke blocks the alpha radiation, the alarm sounds.

• Beta Particles

  • Electron emitted from an atomic nucleus.
  • High average energy.
  • Speed close to the speed of light.
  • Medium relative ionizing ability.
  • Consists of an electron characterized by its high energy and speed.
  • Hazardous, causing ionization of living cells.
  • Able to pass through living cells, potentially causing cancer upon contact with DNA.
  • Can be stopped by an aluminum sheet.
  • Uses: Paper mills and aluminum foil production to test the thickness of sheets. A beta radiation source, placed above the sheets and a radiation reader or Geiger counter, placed under the machine monitor radiation penetration. Low readings indicate the aluminum foil is too thick.

• Gamma Rays

  • High-energy rays (high frequency, short wavelength) with no mass and no charge.
  • Very high average energy.
  • Speed: 3*10^8 m/s.
  • Low relative ionizing ability.
  • Decaying nuclei emit gamma rays to become more stable.
  • Can penetrate a few centimeters of lead or a few meters of concrete.
  • Least ionizing radiation but still very dangerous.
  • Uses: Fighting cancer, sterilizing food, detecting leaking pipes. Gamma rays are placed into the substance flowing through the pipe, and a Geiger-Muller tube above ground measures the radiation given off, identifying leaks.

• Positron

  • Antiparticle of a beta particle, with the same size as an electron but with a positive charge.