Proton repellent

Only protons repel one another by the electric force. 

On solar scales, the change is slow. It takes a billion years for only 0.01 percent of the Sun s mass to metamorphose into beautiful sunshine. The Sun s nuclear reactions are slowed because the positively charged protons repel each other. This repulsion slows down the fusion. If the rate were much quicker, the Sun would explode like a big hydrogen bomb. 

These three isotopes of tellurium are stable. So, their nuclei do not break down spontaneously. Yet, each of these nuclei are composed of 52 protons. How can these positive charges exist so close together Protons repel each other because of their like charges. So, why don t nuclei fall apart There must be some attraction in the nucleus that is stronger than the repulsion due to the positive charges on protons. 

Electrical charges interact in a simple way Like charges repel each other, and unlike charges attract each other. Protons attract electrons, electrons repel electrons, and protons repel protons. 

The figure suggests that this will act as a proton-repelling group only at very short distances, and this is borne out by the following values ... 

Protons repel each other but will nevertheless bind together in the nuclei of atoms under the influence of the strong nuclear force. These protons possess an enormous amount of potential energy, which is achieved at the expense of some mass. According to Einstein s famous equation E=m )y matter and energy are interconvertible. When protons bind together to form the nucleus of an atom, some of their mass is converted into potential energy. As a result, two bound protons will have less mass than two individual protons. This explains why carbon, which has six protons and six neutrons, is less than six times the mass of a deuterium atom, which has one proton and one neutron. 

Most of the ions produced by either thermospray or plasmaspray (with or without the repeller electrode) tend to be very similar to those formed by straightforward chemical ionization with lots of protonated or cationated positive ions or negative ions lacking a hydrogen (see Chapter l).This is because, in the first part of the inlet, the ions continually collide with neutral molecules in the early part of their transit. During these collisions, the ions lose excess internal energy. 

We have discussed the triply charged ion Fe+++ in aqueous solution. Let us consider now the water molecules that are in contact with such an ion, and let Fig. 50a depict one such H2O molecule. The protons in the H2O molecule will be repelled by the large positive charge of the Fe+++ ion—will be so strongly repelled that it is possible that, sooner or later, the thermal agitation will be sufficient to transfer a proton to a... 

Figure 16-2A shows a possible set of the electron-proton distances as they might be seen if it were possible to make an instantaneous photograph. Such distances fix the attractions that cause the chemical bond. But it is well to remember there are also repulsions caused by the approach of the two atoms, as shown in Figure I6-2B. The two electrons repel each other and the two protons do the same. These repulsions tend to push the two atoms apart. Which are more important, the two new attraction... 

What happens when enough NaOH has been added to remove three protons from each Cr(H20)neutral species Cr(H20)3(0H)j, or Cr(0H)3-3H20. This neutral species has no charges to repel other molecules of its own kind so it precipitates. However, as more NaOH is added to this solid phase, one more proton can be removed to produce Crf OJ OH) - and the Cr(0H)3-3H20 dissolves. [In principle, more protons could be removed, perhaps eventually to form Cr(OH) 3, but there is as yet no evidence for this.]... 

Table 10.8 summarizes the properties of common anions in solution. Notice that no cations are listed. Cations cannot readily accept protons, because the positive charge of the cation repels the positive charge of the incoming protons. 

FIGURE 17.14 The protons in a nucleus repel one another electrically, but the strong force, which acts between all nucleons, holds the nucleus together. 

A neutron can get close to a target nucleus more easily than a proton can. Because a neutron has no charge and hence is not repelled by the nuclear charge, it need not be accelerated to such high speeds. An example of neutron-induced transmutation is the formation of cobalt-60, which is used in the radiation treatment of cancer. The three-step process starts from iron-58. First, iron-59 is produced ... 

The charge on a species has a major effect on its ability to donate or accept protons. Remember that opposite electrical charges attract, and like charges repel. An anion is both a better proton acceptor and a poorer proton donor than is a neutral molecule. Likewise, a cation is a poorer proton acceptor and a better proton donor. 

Protonation, if forced upon pyrrole, is found to take place not on nitrogen but on the a-carbon atom (19). This occurs because incorporation of the nitrogen atom s lone pair of electrons into the aromatic 6jre system leaves the N atom positively polarised protons tend to be repelled by it, and are thus taken up by the adjacent a-carbon atom. The basicity situation rather resembles that already encountered with aniline (p. 70) in that the cation (19) is destabilised with respect to the neutral molecule (18a). The effect is much more pronounced with pyrrole, however, for to function as a base it has to lose all aromatic character, and consequent stabilisation this is reflected in its related pKa (-0-27) compared with aniline s of 4-62, i.e. pyrrole is a very weak base indeed. It can in fact function as an acid, albeit a very weak one, in that the H atom of the NH group may be removed by strong bases, e.g. eNH2 the resultant anion (20) then retains the aromatic character of pyrrole, unlike the cation (19) ... 

---