Lesson Notes By Weeks and Term v4 - SHS 2
NUCLEAR PHYSICS
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NUCLEAR PHYSICS
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Subject: Physics
Class: SHS 2
Term: 2nd Term
Week: 20
Grade code: 2.4.1.LI.1
Strand code: 4
Sub-strand code: 2
Content standard code: 2.4.1.CS.1
Indicator code: 2.4.1.LI.1
Theme: ATOMIC AND NUCLEAR PHYSICS
Subtheme: NUCLEAR PHYSICS
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This lesson introduces the fascinating world of the atomic nucleus and the phenomenon of radioactivity. While the word "nuclear" might sound intimidating, its principles are at work all around us. In Ghana, nuclear physics has critical applications, from cancer treatment at hospitals like Korle-Bu and Komfo Anokye to preserving our food crops at the Ghana Atomic Energy Commission (GAEC). By understanding the basics of why some atoms are unstable and how they decay, we can harness their power for medicine, agriculture, and industry, and also understand the need for safety. This lesson lays the foundation for that understanding.
A. The Atomic Nucleus and Stability The nucleus is the tiny, dense core of an atom, containing protons and neutrons. Protons and neutrons are collectively called nucleons. Atomic Number (Z): The number of protons. It defines the element. Mass Number (A): The total number of protons and neutrons (A = Z + N). Nuclide: A specific type of nucleus, represented as `^A_Z X`, where X is the chemical symbol. For example, Carbon-14 is written as `¹⁴₆C`.
Not all nuclei are stable. The stability of a nucleus depends on the ratio of neutrons to protons (N/Z). For light elements, a stable ratio is close to 1:1 (e.g., `¹²₆C` has 6 protons and 6 neutrons). For heavier elements, more neutrons are needed to counteract the electrostatic repulsion between the many protons, so the ratio becomes closer to 1.5:1 (e.g., `²⁰⁸₈₂Pb` has 82 protons and 126 neutrons). Nuclei that fall outside this "band of stability" are unstable.
B. Radioactivity
Definition: Radioactivity is the spontaneous and random disintegration (or decay) of an unstable atomic nucleus, accompanied by the emission of energy in the form of particles or electromagnetic waves (radiation). Spontaneous: The decay process happens on its own, without any external influence like changes in temperature or pressure. Random: It is impossible to predict which specific nucleus in a sample will decay next. We can only talk about the probability of decay.