Nuclear Model and Radioactivity

Nuclear Model and Radioactivity

Exploring the structure of atoms and the phenomenon of radioactivity.

Nuclear Model of the Atom

Understanding the atom's core structure.

Components of the Nucleus

Protons and neutrons form the atom's central nucleus, differing in charge and mass.

Atomic Number and Mass Number

Atomic number defines the number of protons, whereas mass number equates to the sum of protons and neutrons.

Discoveries Leading to the Model

Rutherford's gold foil experiment demonstrated a small, dense nucleus, giving rise to the nuclear model.

Quantum Mechanics and the Nucleus

Quantum theory provides rules governing particles' behavior in the nucleus.

Detection of Radioactivity

Methods and tools for identifying radioactive emissions.

Types of Radiation

Alpha, beta, and gamma radiation differ in mass, charge, and penetrating power.

Detection Instruments

Geiger counters, scintillation detectors, and cloud chambers are used to detect and measure radioactivity.

Radiation Units and Measurement

Radioactivity is measured in becquerels or curies, and radiation absorption in sieverts or rems.

Applications of Radioactivity Detection

Radioactivity monitoring is crucial in medical diagnostics, treatment, and nuclear power safety.

Radioactive Decay

The process by which unstable nuclei release energy.

Types of Decay

Alpha, beta, and gamma decay involve the emission of different particles and energy.

Half-Life

Half-life is the time required for half the quantity of a radioactive substance to undergo decay.

Decay Chains

A series of decays that certain radioactive elements undergo until reaching a stable isotope.

Fission and Fusion

Nuclear fission and fusion involve splitting and combining nuclei, respectively, releasing vast amounts of energy.

Discovery of the Electron

• J.J. Thomson discovered the electron in 1897 using cathode ray tubes.

• Proposed the plum pudding model of the atom.

Rutherford's Gold Foil Experiment

• In 1909, Ernest Rutherford's experiment led to the discovery of the nucleus.

• Disproved Thomson's model by showing atoms are mostly empty space.

Development of the Nuclear Model

• Rutherford proposed a model with a central nucleus surrounded by electrons.

• This laid the groundwork for the modern understanding of the atom.

Bohr's Model

• Niels Bohr introduced quantized orbits for electrons in 1913.

• His model explained atomic emission spectra.

Protons

• Located in the nucleus.

• Carry a positive charge equal in magnitude to the electron's negative charge.

Neutrons

• Also located in the nucleus.

• No net electric charge.

Electrons

• Orbit around the nucleus.

• Negative charge, influencing the chemical properties of an atom.

Atomic Number and Mass

• Atomic number (Z) is the number of protons.

• Atomic mass (A) is the total number of protons and neutrons.

Types of Decay

• Alpha (α) decay: emission of an alpha particle (2 protons and 2 neutrons).

• Beta (β) decay: conversion of a neutron into a proton and an electron.

• Gamma (γ) decay: emission of a gamma photon, usually accompanies α or β decay.

Properties of Radioactive Emissions

• Alpha particles are the least penetrating and can be stopped by paper.

• Beta particles can penetrate skin but are stopped by metal sheets.

• Gamma rays are highly penetrating and require lead or concrete for shielding.

Half-Life

• The time it takes for half of a radioactive sample to decay.

• Isotope-specific, can range from fractions of a second to billions of years.

Radioactive Dating

• Uses the known half-lives of isotopes to estimate the age of materials.

• Carbon-14 dating is a well-known method for organic materials.

Fission

• Splitting of a heavy nucleus into smaller ones with the release of energy.

• Utilized in nuclear reactors and atomic bombs.

Fusion

• Joining of two light nuclei to form a heavier nucleus.

• Powers the sun and stars; potential source for clean energy.

Chain Reactions

• A reaction where the material that starts the reaction is also one of the products.

• Critical for sustaining nuclear reactions, e.g., in a nuclear reactor.

Controlling Nuclear Reactions

• Control rods made of materials like cadmium or boron are used to absorb neutrons.

• Cooling systems transfer heat from the reactor.

Geiger-Müller Tube

• An instrument that detects radiation by counting electric pulses carried by gas ionized by radiation.

Scintillation Detectors

• Use materials that fluoresce when struck by radioactive particles.

• Often used for detecting alpha and beta particles.

Cloud Chambers

• Allow visual observation of the paths of charged particles.

• Consist of a sealed environment that is supersaturated with vapor.

Dosimeters

• Measure an individual's exposure to radiation over time.

• Used to monitor the safety of workers in radioactive environments.

Time, Distance, and Shielding

• Minimize time spent near sources of radiation.

• Maximize distance from the source.

• Use appropriate shielding materials.

Personal Protective Equipment (PPE)

• Lead aprons, gloves, and goggles for protection against radiation exposure.

• Respirators to prevent inhalation of radioactive particles.

Radiation Exposure Limits

• Guidelines that limit occupational exposure to radiation to minimize health risks.

• Dose limits differ for workers, the public, and in medical treatments.

Decontamination Procedures

• Methods to remove or reduce radioactive contamination.

• Include washing, using chemical agents, and restricting access to affected areas.