Atoms strong nuclear force

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... 

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. 

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. 

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 fourth force is the one which is involved in the radioactive jS-decay of atoms and is known as the weak interaction force. Like the strong interaction, this weak interaction force operates over extremely short distances and is the force that is involved in the interaction of very light particle known as leptons (electrons, muons, and neutrinos) with each other and as well as their interaction with mesons, baryons, and nuclei. One characteristic of leptons is that they seem to be quite immune to the strong interaction force. The strong nuclear force is approximately 10 times greater than the Coulombic force, while the weak interaction force is smaller than the strong attraction by a factor of approximately 10. The carrier of the weak interaction force is still a matter of considerable research we will return to this point later. 

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. 

Neutrons serve as nuclear cement holding the atomic nucleus u ether. Protons attract btrth other protons and neutrons by the strong nuclear force, but they also repel other protons by the electric force. Neutrons, on the other hand, have no electric charge and so only attract protons and other neutrons by the. strong nuclear force. The presence of neutrons therefore adds to the attraction among nucleons and helps hold the nucleus toother, as illustrated in Figure 4.14. 

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