Nuclei Class 12 Notes Physics Chapter 13 - CBSE

Chapter : 13

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Topic/Term	Formula	Symbol Representation	Important Points
Radius Nucleus	R = R₀A^1/3 Most of the space in atom is empty. N(θ) ∝(1/sin⁴(θ/2)) where N(θ) = number of α particles θ = scattered angle	R₀ = an empirical constant = 1.1 × 10–15 m A = mass number of atom	Nuclear radius is measured in fermi. 1 fermi = 10^–15 m
Nuclear Density	p= (M/V)	M = mass of nucleus V = volume of nucleus	Density of nuclear matter is of the order of 10¹⁷ kg/m³ Density of nuclear matter is independent of the mass number.
Mass Defect	∆_m = [Zm_p + (A – Z)m_n – M]	Z = atomic number m_p = mass of proton A = atomic mass m_n = mass of neutron M = mass of nucleus
Binding Energy	∆E_b = ∆mc² or ∆E_b = ∆m × 931.5 MeV	∆_m = mass defect	Binding energy is the minimum energy required to break the nucleus into its constituent particles.

Term	Definition / Explanation
Composition of Nucleus	The atomic nucleus consists of two types of elementary particles i.e., protons and neutrons, protons and neutrons are collectively known as nucleons. Atomic number = Number of protons (Z) Mass number (A) = Number of protons (Z) + Number of neutrons (N) Nuclear mass is the total mass of the protons and neutrons measured in amu, 1 atomic mass unit (u) = 931.5 MeV/c²
Nuclear Fission	Fusing two or more lighter nuclei to a single heavy nucleus is known as nuclear fusion. Fusion reactions take place in stars and Hydrogen bomb.