Foundations of Nuclear Physics
What Nuclear Physics Studies
The atomic nucleus
Nuclear physics studies the structure, stability, reactions, and decay of atomic nuclei. A nucleus contains protons and neutrons, collectively called nucleons, and is governed by interactions that are much stronger than electromagnetic forces at femtometer scales.
Size scales
Typical nuclear radii are on the order of with , where is the mass number.
Core quantities
Useful nuclear notation
| Notation | Meaning |
|---|---|
| Nuclide symbol | |
| Mass defect | |
| Binding energy | |
| Half-life |
What quantity uniquely identifies an isotope of an element?
An isotope is defined by the same and a different , so both numbers are needed to specify it.
Correct answer: Both and
Write the relation between mass number, proton number, and neutron number.
The mass number counts all nucleons in the nucleus.
Correct answer: A = Z + N
Forces and Scales
Why nuclei are stable
The strong interaction binds nucleons at short range, overcoming the electric repulsion between protons. Because the strong force saturates, each nucleon interacts strongly only with nearby nucleons, which helps explain why nuclear matter has roughly constant density.
Why does the nuclear force lead to approximately constant nuclear density?
Short-range saturation means each nucleon binds mainly to nearby neighbors, giving nearly constant density across nuclei.
Correct answer: It saturates over short distances
What length scale is typical for nuclear interactions?
Nuclear forces act over distances of order a femtometer.
Correct answer: about 1 fm