Chapter 11: Nuclear Chemistry

Introduction to Nuclear Chemistry

Nuclear chemistry is the study of the structure of atomic nuclei and the changes they undergo. Unlike chemical reactions, which involve electrons, nuclear reactions involve changes in the nucleus and can result in the emission of radiation.

Radioactive Isotopes

Stability of Atomic Nuclei

The stability of an atomic nucleus depends on the ratio of protons to neutrons. A stable nucleus has a balanced ratio, while an unstable nucleus does not.

• Radioactive isotope: An isotope with an unstable nucleus that emits radiation to become more stable.

• Radioactive isotopes can be one or more of the isotopes of an element.

Definition: Isotopes are atoms of the same element with different numbers of neutrons.

Nonradioactive & Radioactive Nuclides

Nuclides are classified as radioactive or nonradioactive based on their stability. The chart (not shown here) typically displays the number of neutrons versus protons, with a 'band of stability' where nonradioactive nuclides are found. Nuclides outside this band are radioactive.

• Nonradioactive nuclides: Stable combinations of protons and neutrons.

• Radioactive nuclides: Unstable combinations that undergo radioactive decay.

Types of Nuclear Radiation

Overview of Nuclear Radiation

Radioactive nuclides emit different types of radiation to become more stable. This process is called radioactive decay. The three main types of nuclear radiation are:

• Alpha (α) particles

• Beta (β) particles

• Gamma (γ) radiation

Alpha (α) Particles

Alpha particles are a combination of 2 protons and 2 neutrons, making them relatively heavy and positively charged.

• Charge: +2

• Mass: Relatively heavy

• Speed: Move slowly

• Penetration: Least penetrating of the three types of radiation

• Symbol: or

Example: Alpha particles can be stopped by a sheet of paper or skin.

Beta (β) Particles

Beta particles are high-energy electrons emitted from the nucleus during radioactive decay.

• Charge: -1

• Mass: Much lighter than alpha particles

• Speed: Move faster than alpha particles

• Penetration: More penetrating than alpha particles, but less than gamma rays

• Symbol: or

Example: Beta particles can penetrate paper but are stopped by materials like aluminum.

Gamma (γ) Radiation

Gamma radiation consists of high-energy electromagnetic waves emitted from a nucleus.

• Charge: No charge

• Mass: No mass

• Penetration: Most penetrating type of radiation

• Symbol:

Example: Gamma rays can penetrate most materials and require thick lead or concrete to block them.

Separation and Penetration of Radiation

Separation of Radiation

When radiation passes through an electric or magnetic field, the different types of radiation are separated based on their charge and mass:

• Alpha particles: Deflected toward the negative plate (positive charge)

• Beta particles: Deflected toward the positive plate (negative charge)

• Gamma rays: Not deflected (no charge)

Radiation Penetration

The ability of radiation to penetrate materials varies by type:

• Alpha (α): Causes surface damage; stopped by paper or clothing

• Beta (β): Penetrates fairly deep into skin; stopped by denser materials such as aluminum

• Gamma (γ): Penetrates through most materials; requires lead or thick concrete for shielding

Example: In medical imaging, gamma rays are used because of their high penetration ability, allowing them to pass through the body and be detected externally.

Additional info: The notes above are based on the provided slides and expanded with standard academic context for clarity and completeness.