Key Concepts: Nuclear Physics

Nuclear Structure

• Nucleus contains protons (positive) and neutrons (neutral), collectively called nucleons.
• Atomic number Z = number of protons. Mass number A = protons + neutrons.
• Isotopes: Same Z, different number of neutrons.

Radioactive Decay

• Alpha (α): Emits ⁴₂He. Z decreases by 2, A decreases by 4.
• Beta (β⁻): A neutron → proton + electron + antineutrino. Z increases by 1.
• Gamma (γ): Emission of a high-energy photon. No change in Z or A.
• Half-life: Time for half the nuclei to decay. N = N₀(½)^(t/t½).

Nuclear Reactions

• Fission: A heavy nucleus splits into lighter nuclei, releasing energy (nuclear reactors, atomic bombs).
• Fusion: Light nuclei combine to form a heavier nucleus, releasing energy (stars, hydrogen bombs).
• Both release energy due to mass defect: E = Δmc² (Einstein's mass-energy equivalence).