βοΈ Understanding Alpha Decay: A Detailed Explanation
Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and transforms into a different atomic nucleus, with a mass number reduced by 4 and an atomic number reduced by 2.
π Learning Objectives
- π― Define alpha decay and its characteristics.
- β’οΈ Explain the components of an alpha particle.
- π’ Apply the alpha decay formula to predict daughter nuclei.
- βοΈ Understand the conservation laws in alpha decay.
π§ͺ Materials
- πΊοΈ Periodic table of elements
- βοΈ Pencil and paper
- π₯οΈ Calculator
- π Textbook or online resources
π₯ Warm-up (5 mins)
- β Briefly review the structure of an atom (protons, neutrons, electrons).
- π€ Ask students what they know about radioactivity.
π¨βπ« Main Instruction
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β’οΈ What is Alpha Decay?
- βοΈ Definition: Alpha decay is a process where an unstable nucleus emits an alpha particle.
- π Alpha Particle: An alpha particle consists of 2 protons and 2 neutrons (a helium nucleus).
- π Result: The parent nucleus transforms into a daughter nucleus with a lower mass and atomic number.
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π’ The Alpha Decay Formula
- βοΈ General Form: The alpha decay formula can be represented as:
$${}_{Z}^{A}X \rightarrow {}_{Z-2}^{A-4}Y + {}_{2}^{4}He$$
- π Where:
- π $X$ is the parent nucleus.
- π $Y$ is the daughter nucleus.
- π ${}_{2}^{4}He$ is the alpha particle.
- π $A$ is the mass number.
- π $Z$ is the atomic number.
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π§ͺ Example of Alpha Decay
- β’οΈ Consider Uranium-238 decaying into Thorium:
$${}_{92}^{238}U \rightarrow {}_{90}^{234}Th + {}_{2}^{4}He$$
- π Explanation:
- π Uranium (U) has an atomic number of 92 and a mass number of 238.
- π After alpha decay, it becomes Thorium (Th) with an atomic number of 90 and a mass number of 234.
- π An alpha particle (Helium) is emitted.
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βοΈ Conservation Laws
- βοΈ Conservation of Mass Number: The sum of mass numbers must be equal on both sides of the equation.
- β‘ Conservation of Atomic Number: The sum of atomic numbers must be equal on both sides of the equation.
π Assessment
- β What is an alpha particle composed of?
- βοΈ Write the alpha decay equation for Polonium-210.
- π’ If Radium-226 undergoes alpha decay, what is the resulting daughter nucleus?