Noble gases, chemical separation

Consider tlie mutual approach of two noble gas atoms. At infinite separation, there is no interaction between them, and this defines die zero of potential energy. The isolated atoms are spherically symmetric, lacking any electric multipole moments. In a classical world (ignoring the chemically irrelevant gravitational interaction) there is no attractive force between them as they approach one another. When tliere are no dissipative forces, the relationship between force F in a given coordinate direction q and potential energy U is... 

The first element in the periodic able, hydrogen, is a reactive substance which forms a great many compounds. The c hemistry of hydrogen is discussed in the following chapter. Helium, the second element, is much different it is a gas with the very striking chemical property that it forms no chemical compounds whatever, but exists only in the free state. Its atoms will not even combine witfi one another to form polyatomic molecules, but remain as separate atoms,in the gas, which is hence described as containing monatomic molecules. Because of its property of remaining aloof from other elements it is called a noble gas. 

The heavy black line in Fig. 20.1 separates the metals from the nonmetals, except for one case. Flydrogen, which appears on the metal side, is a nonmetal. Some elementsjust on either side of this line, such as silicon and germanium, exhibit both metallic and non-metallic properties. These elements are often called metalloids, or semimetals. The fundamental chemical difference between metals and nonmetals is that metals tend to lose their valence electrons to form cations, which usually have the valence electron configuration of the noble gas from the preceding period. On the other hand, nonmetals tend to gain electrons to form anions that exhibit the electron configuration of the noble gas in... 

Electrons fill each sublevel in accordance with Hand s rule, which states that electrons in orbitals of one sublevel tend to have the same spin. This means that electrons add to empty orbitals so long as they are available. This is reasonable, since electrons repel each other and would prefer to be in separate orbitals (as far from one another as possible). The electronic structure of N, Ti, and Mn can be designated as shown in Figure 2.2. Electrons in the p sublevel of N and in the d sublevel of Ti and Mn are impaired. It is not necessary to list all of the sublevels as is done in the figure only the electrons beyond those of the preceding noble gas (the valence electrons ) are generally shown, since these are the ones involved in chemical bonding. One final point is that, for later use, it is more convenient to list the id sublevel before the 4, the 4d and 4/ before the 5s, etc. 

The eighth edition in 1906 was the last edition published before Mendeleevs death. All the notes were separated from the main text and placed in the second half of the book. He argued for the possibility of chemical ether as an extremely light element in the noble-gas group, which he thought could explain radioactivity. ... 

---