Atomic Structure and Radioactive Decay
This section provides a detailed overview of atomic structure and the fundamentals of radioactive decay, essential for understanding radioactivity Physics notes.
The atomic structure is explained, detailing the properties of protons, neutrons, and electrons:
- Protons: Positive charge, relative mass of 1, located in the nucleus
- Neutrons: No charge, relative mass of 1, located in the nucleus
- Electrons: Negative charge, relative mass of 1/2000, located in outer shells
Highlight: The majority of an atom's mass is concentrated in its nucleus.
The concepts of mass number and atomic number are introduced:
- Mass number: Total number of protons and neutrons
- Atomic number: Number of protons in a nuclide
Radioactive decay is described as the process by which unstable nuclei break down or rearrange to form stable nuclei, emitting nuclear radiation.
Definition: Radioactive decay is a random process that occurs continuously, regardless of external factors like temperature or pressure.
Three types of radioactive decay are explained in detail:
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Alpha Decay (α):
- Emits alpha particles (2 protons and 2 neutrons)
- Weakly penetrating but highly ionizing
- Deflected by electric fields due to positive charge
-
Beta Decay (β):
- Emits beta particles (high-speed electrons)
- Moderately penetrating and ionizing
- Deflected by electric fields due to negative charge
-
Gamma Decay (γ):
- Emits high-energy electromagnetic waves
- Highly penetrating but weakly ionizing
- Not deflected by electric fields
Example: Alpha particles can be stopped by a few centimeters of air or a piece of paper, while gamma rays require thick lead or concrete for shielding.
The concept of isotopes is introduced, explaining that isotopes of an element have the same number of protons and electrons but different numbers of neutrons.
Vocabulary: A radioisotope is an isotope that is radioactive, such as carbon-14 used in carbon dating.
Equations for alpha and beta decay are provided, demonstrating changes in mass and atomic numbers during these processes.
