1.2 Fundamental concepts of radioactivity

Radioactive decay is a fundamental process in radiochemistry. It happens when unstable atomic nuclei emit radiation, transforming into different nuclides. This spontaneous process can't be influenced by external factors and occurs at a rate proportional to the number of radioactive nuclei present.

Half-life and decay constant are key concepts in understanding radioactivity. Half-life is the time it takes for half of a radioactive substance to decay, while the decay constant represents the probability of decay per unit time. These concepts help us predict and measure radioactive behavior.

Radioactive Decay and Half-Life

Fundamentals of Radioactive Decay

Top images from around the web for Fundamentals of Radioactive Decay

• 

  31.5 Half-Life and Activity – College Physics View original

  Is this image relevant?

• 

  Radioactive Decay | Chemistry: Atoms First View original

  Is this image relevant?

• 

  Radioactive decay - wikidoc View original

  Is this image relevant?

• 

  31.5 Half-Life and Activity – College Physics View original

  Is this image relevant?

• 

  Radioactive Decay | Chemistry: Atoms First View original

  Is this image relevant?

1 of 3

Top images from around the web for Fundamentals of Radioactive Decay

• 

  31.5 Half-Life and Activity – College Physics View original

  Is this image relevant?

• 

  Radioactive Decay | Chemistry: Atoms First View original

  Is this image relevant?

• 

  Radioactive decay - wikidoc View original

  Is this image relevant?

• 

  31.5 Half-Life and Activity – College Physics View original

  Is this image relevant?

• 

  Radioactive Decay | Chemistry: Atoms First View original

  Is this image relevant?

1 of 3

• Radioactive decay occurs when an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves
• This process happens spontaneously and cannot be influenced by external factors (temperature, pressure, or chemical reactions)
• During radioactive decay, the nucleus transforms into a different nuclide, which may be stable or radioactive
• The rate of radioactive decay is proportional to the number of radioactive nuclei present in a sample

Half-Life and Decay Constant

• Half-life ($t_{1/2}$) represents the time required for half of the original amount of a radioactive substance to decay
  • For example, if a sample has a half-life of 10 days, after 10 days, half of the original amount will have decayed, and after another 10 days, half of the remaining amount will have decayed
• The decay constant ($\lambda$) is the probability per unit time that a nucleus will decay
  • It is related to the half-life by the equation: $\lambda = \frac{\ln 2}{t_{1/2}}$
• The number of radioactive nuclei ($N$) remaining at a given time ($t$) can be calculated using the equation: $N(t) = N_0 e^{-\lambda t}$, where $N_0$ is the initial number of radioactive nuclei

Activity and Its Measurement

• Activity ($A$) is the rate of radioactive decay, measured in becquerels (Bq) or curies (Ci)
  • One becquerel is defined as one decay per second
  • One curie is equal to $3.7 \times 10^{10}$ becquerels
• Activity can be calculated using the equation: $A = \lambda N$
• The activity of a radioactive sample decreases exponentially over time, following the same pattern as the number of radioactive nuclei
• Measuring the activity of a sample can be done using various instruments (Geiger counters, scintillation detectors, or ionization chambers)

Isotopes and Nuclear Stability

Understanding Isotopes

• Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons
  • For example, carbon-12, carbon-13, and carbon-14 are isotopes of carbon, with 6, 7, and 8 neutrons, respectively
• Isotopes have the same chemical properties but may have different physical properties (radioactivity, half-life, or atomic mass)
• Isotopes can be stable or unstable (radioactive), depending on the ratio of protons to neutrons in their nuclei

Factors Affecting Nuclear Stability

• Nuclear stability is influenced by the number of protons and neutrons in the nucleus
• Stable nuclei typically have a specific ratio of protons to neutrons, known as the "line of stability"
  • For light elements, the most stable nuclei have an equal number of protons and neutrons
  • For heavier elements, the most stable nuclei have more neutrons than protons
• Nuclei with too many or too few neutrons relative to protons are unstable and undergo radioactive decay to achieve greater stability

Radioactive Series

• A radioactive series, also known as a decay chain, is a sequence of radioactive decays that occurs until a stable isotope is reached
• There are four main radioactive series found in nature: the thorium series, the neptunium series, the uranium series, and the actinium series
  • Each series starts with a long-lived parent isotope and ends with a stable lead isotope
• The decay products within a radioactive series have characteristic half-lives and decay modes (alpha, beta, or gamma emission)
• Understanding radioactive series is important for applications (radiometric dating, nuclear waste management, or environmental monitoring)

Types of Radiation

Alpha, Beta, and Gamma Radiation

• Alpha radiation consists of alpha particles, which are helium nuclei (two protons and two neutrons)
  • Alpha particles have a positive charge and are relatively heavy, limiting their penetrating power
  • They can be stopped by a sheet of paper or a few centimeters of air
• Beta radiation consists of beta particles, which are high-energy electrons or positrons emitted from the nucleus
  • Beta particles have a negative charge (electrons) or a positive charge (positrons) and are lighter than alpha particles
  • They can penetrate deeper than alpha particles but can be stopped by a few millimeters of aluminum or plastic
• Gamma radiation is high-energy electromagnetic radiation emitted from the nucleus
  • Gamma rays have no charge or mass and have the highest penetrating power among the three types of radiation
  • They can penetrate deeply into matter and require dense materials (lead or concrete) for effective shielding