atomkerne

Atomkerne are the cores of atoms, consisting of protons and neutrons, collectively called nucleons. They carry almost all of the atom's mass and determine its identity through the number of protons, the atomic number Z. The nucleus has a diameter in the order of 1 femtometer and is held together by the strong nuclear force acting over a short range, while electrostatic repulsion between protons opposes binding in heavier nuclei. The total number of protons is the atomic number, and the total nucleons count equals the mass number A. Isotopes differ in neutron number N = A − Z.

The binding energy per nucleon varies with A, peaking near iron and nickel, which accounts for the relative stability of mid-sized nuclei. Nuclear structure is described by models such as the liquid drop model, which explains binding energy and fission, and the shell model, which explains magic numbers of protons or neutrons that yield extra stability. Nuclei can undergo radioactive decay and reactions, emitting alpha particles (helium nuclei), beta particles, or gamma rays, and they participate in fusion and fission processes.

Historically, the existence of the nucleus was established by Rutherford in 1911, followed by Chadwick’s discovery of the neutron in 1932. Today, atomkerne are central to fields ranging from nuclear energy and medicine to archaeology and astrophysics, enabling techniques such as radiometric dating and PET imaging. Knowledge of nuclei continues to advance through experimental measurements and theoretical models that probe their energy spectra, shapes, and reaction behavior.