Chapter 5: Nuclear Chemistry – Study Notes

Chapter 5: Nuclear Chemistry

Introduction to Nuclear Chemistry

Nuclear chemistry is the study of the structure of atomic nuclei and the changes they undergo. It has important applications in medicine, energy production, and scientific research. Radiation technologists use nuclear chemistry in hospitals and imaging centers to diagnose and treat various medical conditions.

Natural Radioactivity

Definition and Occurrence

• Radioactivity is the spontaneous emission of particles or energy from unstable atomic nuclei to become more stable.

• Most naturally occurring isotopes of elements with atomic numbers up to 19 have stable nuclei.

• Elements with atomic numbers 20 and higher often have one or more isotopes with unstable nuclei, where nuclear forces cannot offset proton repulsions.

Radioisotopes

• A radioisotope is an isotope with an unstable nucleus that emits radiation.

• Radioisotopes can be one or more isotopes of an element and are identified by their mass number (e.g., Carbon-14, 14C).

• Example: Carbon-14 (14C) is used in archeological dating and has a mass number of 14 and atomic number of 6.

Stable and Radioactive Isotopes

Some elements have both stable and radioactive isotopes. The following table summarizes examples:

Element	Stable Isotopes	Radioactive Isotopes
Magnesium	24Mg	23Mg, 27Mg
Iodine	127I	125I, 131I
Uranium	None	235U, 238U

Types of Radiation Emitted

Radioisotopes emit several types of radiation as they decay to become more stable:

• Alpha (α) particles: Identical to a helium nucleus, 4He

• Beta (β) particles: High-energy electrons, 0−1e

• Positrons (β+): Positive electrons, 0+1e

• Gamma (γ) rays: Pure energy, 00γ

Alpha Particles

• Identical to a helium nucleus (4He or α)

• Composed of 2 protons and 2 neutrons

• Mass number: 4

• Charge: 2+

• Low energy compared to other radiation particles

Beta Particles

• High-energy electrons (0−1e or β)

• Mass number: 0

• Charge: 1−

• Formed when a neutron changes into a proton and an electron in an unstable nucleus

Positrons

• Positive electrons (0+1e or β+)

• Mass number: 0

• Charge: 1+

• Formed when a proton changes into a neutron and a positron in an unstable nucleus

Gamma Rays

• High-energy electromagnetic radiation (00γ or γ)

• Mass number: 0

• Charge: 0

• Emitted from an unstable nucleus to give a more stable, lower-energy nucleus

Summary Table: Some Forms of Radiation

Type of Radiation	Symbol	Mass Number	Charge
Alpha Particle	42He, α	4	2+
Beta Particle	0−1e, β	0	1−
Positron	0+1e, β+	0	1+
Gamma Ray	00γ, γ	0	0
Proton	11H, p	1	1+
Neutron	10n, n	1	0

Biological Effects of Radiation

Ionizing Radiation and Its Effects

• Ionizing radiation can damage or destroy molecules in living cells.

• Cells most sensitive to radiation include rapidly dividing cells in bone marrow, skin, reproductive organs, and cancer cells.

• Cancer cells are highly sensitive to radiation; thus, large doses are used in cancer treatment.

• Normal tissue divides more slowly and is less affected by radiation.

• Radiation exposure can cause malignant tumors, leukemia, anemia, and genetic mutations.

Radiation Protection

Shielding and Safety Measures

• Alpha particles: Protected by paper and clothing

• Beta particles: Protected by a lab coat or gloves

• Gamma rays: Require a lead shield or thick concrete wall

• General safety: Limit time near sources and increase distance from them

Penetration and Shielding Table

Property	Alpha (α) Particle	Beta (β) Particle	Gamma (γ) Ray
Typical Distance in Air	2–4 cm	200–300 cm	500 m
Tissue Depth	0.01 mm	4–5 mm	50 cm or more
Shielding	Paper, clothing	Heavy clothing, lab coats, gloves	Lead, thick concrete
Typical Source	Radium-226	Carbon-14	Technetium-99m

Examples of Shielding

• Heavy clothing: Protects against alpha and beta particles

• Paper: Protects against alpha particles

• Lead: Protects against alpha, beta, and gamma radiation

• Lab coat: Protects against alpha and beta particles

• Thick concrete: Protects against alpha, beta, and gamma radiation

Practice Problems and Solutions

Mass Number and Charge of Radiation Types

• Alpha particle: Mass number = 4, Charge = 2+

• Positron: Mass number = 0, Charge = 1+

• Beta particle: Mass number = 0, Charge = 1−

• Neutron: Mass number = 1, Charge = 0

• Gamma ray: Mass number = 0, Charge = 0

Shielding Practice

• Heavy clothing: Alpha, beta

• Paper: Alpha

• Lead: Alpha, beta, gamma

• Lab coat: Alpha, beta

• Thick concrete: Alpha, beta, gamma

Additional info: Nuclear chemistry is foundational for understanding radioactive decay, nuclear reactions, and their applications in medicine and industry. The notes above cover the essential concepts and safety considerations for introductory college-level study.