• summary_type: revision
• word_count: 180

Essential formulas: R = R_0A^(1/3) (R_0 = 1.2 fm). Delta_m = Zm_p + (A-Z)m_n - M. BE = Delta_m x 931.5 MeV. N(t) = N_0e^(-lambdat). t_(1/2) = 0.693/lambda. tau = 1.44t_(1/2). Activity A = lambda*N. 1 u = 931.5 MeV/c^2. Alpha: Z-2, A-4. Beta-minus: Z+1, A same. Gamma: Z same, A same.

JEE strategy by question type: (1) Radius ratio: use R proportional to A^(1/3). (2) Binding energy: compute mass defect, multiply by 931.5. (3) Decay problems: identify n = t/t_(1/2); if integer, use N_0/2^n; otherwise use exponential. (4) Successive decays: track Z and A through each step. (5) Q-value: sum reactant masses minus product masses, times 931.5. (6) Decay chain: alpha count = Delta_A/4, then balance Z for beta count. Common traps: confusing remaining with decayed fraction, forgetting neutrino in beta decay energy sharing, using atomic vs nuclear masses inconsistently, and assuming alpha particle carries all Q-value energy (it carries only (A-4)/A fraction).