Nuclear Physics Fundamentals: Forces, Isotopes, and Decay

Nuclear Physics Fundamentals

The atomic nucleus is formed by nucleons (protons and neutrons). The atomic number (Z) defines the mass.

Nuclide Classifications

• Isotopes: Nuclides with the same number of protons but a distinct number of neutrons.
• Isobars: Nuclides with the same mass number (A) but a distinct number of protons and neutrons.
• Isotones: Nuclides with the same number of neutrons but a different number of protons.

Fundamental Forces of Nature

• Gravitational Force: Exerted between two particles with mass. It is always attractive and responsible for the existence of planets and stars. It is a weak, long-range interaction.
• Electromagnetic Force: Exerted between two electrically charged particles. It can be attractive or repulsive and is responsible for the structure of atoms and molecules. It is stronger than gravity and acts at distances greater than 10^-15m.
• Strong Nuclear Force: Responsible for the cohesion of the nucleus by holding nucleons together. It is very intense at nuclear distances but practically zero at distances greater than 10^-15m.
• Weak Nuclear Force: Responsible for the beta disintegration of unstable nuclei. It is weaker than the strong and electromagnetic forces but stronger than gravity. It acts at very short ranges, practically zero beyond 10^-17m.

Strong Interaction Features

Occurs between protons and neutrons. It is short-range (10^-15m), non-central, attractive at distances greater than 10^-16m, and repulsive at very short distances.

Mass Defect and Binding Energy

The mass of a nuclide is less than the sum of the mass of its individual nucleons. The mass defect (Δm) is calculated as: Δm = M - (Zmp + Nmn), where mp is the proton mass (1.67252 × 10^-27kg) and mn is the neutron mass (1.67482 × 10^-27kg).

Binding Energy: The energy required to form a nuclide, calculated using Einstein's equation: E = mc².

Radioactivity and Decay

• Half-life: The average time taken for a substance to decay.
• Period of Semi-disintegration: The time required for half of an initial amount of substance to disintegrate.
• Radioactive Activity: The number of disintegrations per second.

Types of Radiation

• Alpha Radiation: Emission of a ⁴₂He nucleus, resulting in a nuclide with 2 fewer protons and 2 fewer neutrons.
• Beta Radiation: Emission of electrons where a neutron becomes a proton (or vice versa), changing the atomic number while the mass number remains unchanged.
• Gamma Radiation: Emission of energy from an excited nucleus returning to a normal state.

Nuclear Reactions

• Fusion: The combining of two nuclei, such as deuterium.
• Fission: A process where a nucleus captures a neutron, becomes unstable, and splits.