Nuclei Mind Map

The nucleus is the small, dense, positively charged central part of an atom containing Z protons and N neutrons. The mass number is A = Z + N, and the nuclear radius is approximately R = R0 A^(1/3), where R0 is about 1.2 fm.

When a question gives isotope notation, first identify A and Z, then calculate N = A - Z. For radius questions, compare using R proportional to A^(1/3), not directly proportional to A.

Mass-energy equivalence states that mass and energy are related by E = mc^2. In a nucleus, the mass defect is the difference between the total mass of separated nucleons and the actual nuclear mass, and the corresponding binding energy is the energy needed to separate the nucleus into its nucleons.

For stability comparison, use binding energy per nucleon, not total binding energy alone. For energy release, compare binding energy before and after the reaction.

Nuclear force is the strong attractive force between nucleons that binds protons and neutrons inside the nucleus. It is short-ranged, very strong within nuclear distances, approximately charge-independent, and shows saturation.

In reasoning answers, mention both strength and range. Saying only that nuclear force is strong is incomplete because its short range is equally important.

Radioactivity is the spontaneous transformation of an unstable nucleus with emission of alpha particles, beta particles, or gamma radiation. The number of undecayed nuclei follows N = N0 e^(-lambda t), and half-life is T1/2 = ln 2/lambda.

For alpha and beta decay, write changes in A and Z before naming the daughter nucleus. For half-life numericals, count the number of half-lives using t/T1/2.

Nuclear fission is the splitting of a heavy nucleus into two medium-mass nuclei with release of energy and usually neutrons. Nuclear fusion is the combination of light nuclei to form a heavier nucleus with release of energy under extremely high temperature and pressure conditions.

When comparing fission and fusion, write reactants, products, condition, chain reaction possibility, and binding-energy explanation. Avoid giving only everyday uses.