What is nuclear power in an atom

Core models

Historical ideas for the structure of the atomic nucleus

  • In 1911, Rutherford only spoke of the fact that there is an almost punctiform positive central charge in the center of the atom. Later he used the term "nucleus" for this central charge.
  • In 1920 Rutherford called the nucleus of the hydrogen atom "proton".
  • Some physicists assumed that heavier atoms are made up of hydrogen atoms (one proton in the nucleus, one electron in the atomic shell). However, this would have led to contradictions with the knowledge that was already available at that time about the mass and the number of electrons of atoms.
    Therefore, Rutherford (1920) suspected another core building block in addition to the proton, the neutron. This particle should have roughly the same mass as the proton, but should not carry any electrical charge. The core building blocks proton and neutron are also referred to by the umbrella term Nucleon.
  • In 1932 a student of Rutherford, namely J. Chadwick, was able to detect the neutron.

The nuclear force holds the nucleons together

The following qualitative knowledge about nuclear power was obtained mainly from experiments in which nucleons were scattered on nucleons. A simple formula such as that found for the Coulomb force or the gravitational force does not exist for the nuclear force.

With every atom (exception: hydrogen) there are several protons in the nucleus. Now we know that protons repel each other due to the acting Coulomb force, the stronger the closer they are. With the small core diameter, this repulsive force between the protons is considerable. In order for a nucleus to be stable, i.e. for the protons to hold together, there must be another, attractive force in addition to the repulsive Coulomb force, which ensures the cohesion of the protons. This force is called the Nuclear power (The deviation of the scattering distribution of high-energy α-particles from the scattering distribution predicted by the pure Coulomb interaction already indicates the action of a force between the core components, if these only come close enough).

Properties of nuclear power

In the following some properties of the nuclear force that acts between the nucleons are summarized. The more precise knowledge about the nuclear force was obtained essentially from experiments in which nucleons were scattered by nucleons:

  • The attractive effect of the nuclear force between the nucleons only starts when the distance between the nucleon centers is approx. 2 fm.
    Note: 1 fm (femtometer) = 10-15m
  • If the nucleon centers come closer than about 0.5 fm, a strong repulsive force sets in (this "hard core force" prevents the nuclei from collapsing).

    The two statements above can also be represented by the course of the force between two nucleons, as sketched on the right, as a function of the distance r between their centers. According to this, the attractive nuclear force is greatest at approx. 1.3 fm and clearly outweighs the repulsive Coulomb force (only acting between the protons).
  • The nuclear force is charge-independent, i.e. it is the same for a neutron-neutron, neutron-proton or proton-proton interaction. Of course, the Coulomb repulsion also has an effect on the proton-proton interaction.