Nucleus strong nuclear force

Electrical repulsion between protons should cause a nucleus that contains more than one proton to fly apart. In Section 2H. we describe how the third type of fundamental force, called the strong nuclear force, acts within nuclei and generates enough attraction among nuclear particles to hold nuclei together. 

As described in Chapter 2, nuclei with more than one nucleon are held together by the strong nuclear force. Energy must be provided to overcome this force and remove a nucleon from a nucleus. This energy is called the nuclear binding energy. 

Neutron capture always is exothermic, because the neutron is attracted to the nucleus by the strong nuclear force. Consequently, neutron capture generates a product nuclide in a metastable, excited state. These excited nuclei typically lose energy by emitting either y rays or protons ... 

Strong Nuclear Force force responsible for binding the nucleons of an atom s nucleus together... 

The more protons there are in a nucleus, the more neutrons are needed to help balance the repulsive electric forces. For light elements, it is sufficient to have about as many neutrons as protons. The most common isotope of carbon, carbon-12, for instance, has six protons and six neutrons. For large nuclei, more neutrons than protons are required. Remember that the strong nuclear force diminishes rapidly with increasing distance between nucleons. Nucleons must be practically touching in order for the strong nuclear force to be effective. Nucleons on opposite sides of a large atomic nucleus are not as attracted to one another. The electric force, however, does not diminish by much across the... 

Was this yow answer Two protons in a nucleus repel each other by the electric force, true, but they also attract each other by the strong nuclear force. Both forces act simultaneously. So long as the attractive strong nuclear force is more influential than the repulsive electric force, the protons remain together. Under conditions where the electric force overcomes the strong nuclear force, the protons fly apart. 

The presence of neutrons helps hold the atomic nucleus together by increasing the effect of the attractive strong nuclear force, represented by the single-headed arrows. 

The second reason the stabilizing effect of neutrons is limited is that any proton in the nucleus is attracted by the strong nuclear force only to adjacent protons but is electrically repelled by all other protons in the nucleus. As more and more protons are squeezed into the nucleus, the repulsive electric forces increase substantially. For example, each of the two protons in a helium nucleus feels the repulsive effect of the other. Each proton in a nucleus containing 84 protons, however, feels the repulsive effects of 83 protons The attractive nuclear force exerted by each neutron, however, extends only to its immediate neighbors. The size of the atomic nucleus is therefore limited. This in turn limits the number of possible elements in the periodic table. It is for this reason that all nuclei having more than 83 protons are radioactive. Also, the nuclei of the heaviest elements produced in the laboratory are so unstable (radioactive) that they exist for only fractions of a second. 

Think of the enormous external force required to pull a nucleon out of the nucleus through a distance sufficient to overcome the attractive strong nuclear force, comically represented in Figure 4.28. As per the word equation for work just given, enormous force exerted through a distance means that enormous work is required. This work is energy that has been added to the nucleon. 

A strong nuclear force carried by particles called gluons binds together protons and neutrons in an atomic nucleus. When an atom is split, energy from the atomic nucleus is released. The amount of energy released is predicted by the equation, e = me2. 

The strong nuclear force overcomes electric repulsion and holds neutrons and protons together in a nucleus. 

In the nucleus, the nuclear force acts only over a distance of a few nucleon diameters. Arrows describe magnitudes of the strong force acting on the protons. 

Every atom has an extremely dense nucleus that contains most of the atom s mass. The nucleus contains positively charged protons and neutral neutrons, both of which are referred to as nucleons. You may have wondered how protons remain in the densely packed nucleus despite the strong electrostatic repulsion forces produced by the positively charged particles. The answer is that the strong nuclear force, a force that acts only on subatomic particles that are extremely close together, overcomes the electrostatic repulsion between protons. 

To a certain degree, the stability of a nucleus can be correlated with its neu-tron-to-proton (n/p) ratio. For atoms with low atomic numbers (< 20), the most stable nuclei are those with neutron-to-proton ratios of 1 1. For example, helium ( He) has two neutrons and two protons, and a neutron-to-pro-ton ratio of 1 1. As atomic number increases, more and more neutrons are needed to produce a strong nuclear force that is sufficient to balance the electrostatic repulsion forces. Thus, the neutron-to-proton ratio for stable atoms gradually increases, reaching a maximum of approximately 1.5 1 for the largest atoms. An example of this is lead With 124 neutrons and 82... 

The strong nuclear force acts on protons and neutrons within a nucleus to hold the nucleus together. 

However, we know, from high-energy physics experiments, that the interaction potential between a neutron (of typical energy ca lO MeV) and the nucleus is not weak but involves the strong nuclear force of ca 36 MeV. We can, however, avoid the nuclear force problem by searching for a new form for the interaction potential. The required potential must give S-wave solutions to the final neutron wavefunction when the Bom approximation is applied. 

In a similar maimer, patterns of nuclear stability, results of nuclear reactions and spectroscopy of radiation emitted by nuclei have yielded information which helps us develop a picture of nuclear structure. But the situation is more complicated for the nucleus than for the atom. In the nucleus there are two kinds of particles, protons and neutrons, packed close together, and there are two kinds of forces - the electrostatic force and the short range strong nuclear force. This more complex situation has caused slow progress in developing a satisfactory model, and no single nuclear model has been able to explain all the nuclear ph omena. 

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