Nuclear Binding Energy and Nuclear Reactions

This page delves into the concepts of nuclear binding energy, mass defect, and nuclear reactions such as fission and fusion.

Nuclear binding energy is the energy required to separate a nucleus into its constituent nucleons. It is closely related to the concept of mass defect, which is the difference between the mass of a nucleus and the sum of its individual nucleon masses.

Definition: The binding energy of nucleus is the energy required to separate a nucleus into its constituent nucleons.

Vocabulary: Mass defect refers to the difference between the mass of a nucleus and the sum of its individual nucleon masses.

The page explains that mass and energy are interchangeable at the nuclear level, following Einstein's famous equation E = mc². It introduces the atomic mass unit (u) as a convenient measure for atomic masses, with 1u equivalent to 931.5 MeV of energy.

Example: A change in 1u of mass is equivalent to 931.5 MeV of energy released.

The concept of binding energy per nucleon is introduced, which is crucial for understanding nuclear stability and the potential for nuclear reactions.

Definition: Binding energy per nucleon is the binding energy of a nucleus divided by the number of nucleons in the nucleus.

The page then discusses nuclear fission and fusion:

Nuclear Fission:

• Splitting of a large nucleus into two daughter nuclei
• Occurs in large, unstable nuclei or can be induced
• Releases energy because the smaller daughter nuclei have a higher binding energy per nucleon

Nuclear Fusion:

• Joining of two small nuclei to form one larger nucleus
• Occurs in small nuclei
• Releases more energy than fission but requires extremely high temperatures

Highlight: Nuclear fusion vs fission energy output: Fusion releases more energy than fission, but it can only happen at extremely high temperatures (in stars).

The page concludes with a graph of binding energy per nucleon against nucleon number, which helps identify whether an element can undergo fusion or fission.

Example: Elements smaller than iron can undergo fusion, while elements larger than iron can undergo fission.

Nuclear Radiation Mechanisms and Background Radiation

This page covers the mechanisms of nuclear fusion in more detail, as well as the concept of background radiation and its sources.

Nuclear Fusion Mechanism:

• Requires extremely high temperatures to overcome electrostatic repulsion between nuclei
• Needs high densities of matter to ensure enough colliding protons for fusion to occur

Highlight: Fusion can only occur at extremely high temperatures because a massive amount of energy is required to overcome the electrostatic repulsion between nuclei.

Background Radiation:

• Constantly present in our environment
• Must be accounted for when measuring radiation from a source

Definition: Background radiation refers to the naturally occurring radiation that is always present in the environment.

Sources of background radiation include:

• Radon gas released from rocks
• Artificial sources (nuclear weapons testing, nuclear accidents)
• Cosmic rays from space
• Naturally occurring radioactive isotopes in rocks

The page then discusses different types of radiation:

Alpha (α) Radiation:

• Helium nucleus (2 protons and 2 neutrons)
• Highly ionizing
• Short range in air (2-10 cm)
• Stopped by paper

Beta (β) Radiation:

• Fast-moving electron
• Weakly ionizing
• Range in air around 1 meter
• Stopped by aluminum foil (about 3 mm thick)

Gamma (γ) Radiation:

• Electromagnetic wave
• Very weakly ionizing
• Infinite range, follows inverse-square law
• Requires several meters of concrete or inches of lead to stop

The page also covers nuclear equations for alpha and beta decay:

Example: Alpha decay equation: AXZ → A-4YZ-2 + 4α2 Example: Beta-minus decay equation: AXZ → AYZ+1 + β- + v̄e

An experiment to determine the type of radiation emitted by a source is described, using a Geiger-Müller tube and various absorbers.

The random nature of radioactive decay is explained, introducing the decay constant (λ) and how it relates to the change in the number of nuclei over time.

Definition: The decay constant (λ) is the probability of a nucleus decaying per unit time.