Second-period elements, characteristics

The unique properties of carbon relate to its position in the periodic table. As a second-period element, carbon atoms are relatively small. Therefore, it can easily form the double and triple bonds that are rare in the compounds of related elements, such as silicon. As a Group IV element, carbon can form four bonds, which is more than the other second-period elements this characteristic gives it wide... 

Figure 7 A portion of Babaev s periodic system. Each compartment y > 0 contains more than one molecule due to the fact that hydrogen-containing species may be included and also (y > 1) due to proton shifting (e.g., from Be2 to LiC). These different species could be shown if additional dimensions were available. Molecules with odd numbers of electrons are not shown. All entries are from the second period of the chart of the elements entries including atoms from other periods could be displayed if other additional dimensions were invoked. Various kinds of isomers could be exhibited if yet more dimensions were utilized. The right-hand edge of this table contains species at the limit of stability the addition of any more electrons results in instability. However, if atoms from higher periods are allowed, then some species with Euler characteristic >2 can be stable. Some of them are mentioned in the text (Adapted from Babaev and Hefferlin 1996).

To answer this question, we need to consider the different types of valence orbitals characteristic of second- and third-period elements. The second-row elements have 2s and 2p valence orbitals, and the third-row elements have 3s, 3p, and 3d orbitals. The 3s and 3p orbitals fill with electrons in going from sodium to argon, but the 3d orbitals remain empty. For example, the valence orbital diagram for a sulfur atom is... 

Then we have some key pieces of information, two of which are the van der Waals characteristics of helium and neon. (Larger rare gas atoms also become important when one considers atoms further down in the periodic table.) How closely can we approximate the van der Waals characteristics of hydrogen with those of helium And how closely can we approximate the van der Waals properties of carbon with those of neon We would expect that carbon and neon would be rather similar in their properties. We know that as we go across the periodic table from left to right, the van der Waals radii of the atoms become smaller, and we know by approximately how much. The value of e for carbon would be expected to be similar to that for neon. The polarizabilities of atoms decrease somewhat as we go to the right in the periodic table. The number of electrons may increase, but they are more tightly held. But we also know that there is a big difference in polarizability between the first-row elements and second-row elements. To a first approximation, the first-row elements are similar. On the other hand, one expects a sizable difference between hydrogen and helium. 

These elements formed Group IIB of Mendeleef s original periodic table. As we have seen in Chapter 13, zinc does not show very marked transition-metaf characteristics. The other two elements in this group, cadmium and mercury, lie at the ends of the second and third transition series (Y-Cd, La-Hg) and, although they resemble zinc in some respects in showing a predominantly - - 2 oxidation state, they also show rather more transition-metal characteristics. Additionally, mercury has characteristics, some of which relate it quite closely to its immediate predecessors in the third transition series, platinum and gold, and some of which are decidedly peculiar to mercury. 

Antimony [7440-36-0J, Sb, belongs to Group 15 (VA) of the periodic table which also includes the elements arsenic and bismuth. It is in the second long period of the table between tin and tellurium. Antimony, which may exhibit a valence of +5, +3, 0, or —3 (see Antimony compounds), is classified as a nonmetal or metalloid, although it has metallic characteristics in the trivalent state. There are two stable antimony isotopes that ate both abundant and have masses of 121 (57.25%) and 123 (42.75%). 

While there is little reason seriously to consider Teudt s first conception, yet there is some justification for his second one, because the osmophoric elements are all grouped together in the periodic table and are therefore likely to have a fundamental common characteristic. 

Osmium is found in group 8 (VIII) of the periodic table and has some of the same chemical, physical, and historical characteristics as several other elements. This group of similar elements is classed as the platinum group, which includes Ru, Rh, and Pd of the second transition series (period 5) and Os, Ir, and Pt of the third series of transition metals (period 6). 

Indium has one odd characteristic in that in the form of a sheet, like the metal tin, it will emit a shrieking sound when bent rapidly. Indium has some of the characteristics of other metals near it in the periodic table and may be thought of as an extension of the second series of the transition elements. Although it is corrosion-resistant at room temperature, it will oxidi2e at higher temperatures. It is soluble in acids, but not in alkalis or hot water. 

The valence electron configuration of the atoms of the Group 2 elements is ms2, where n is the period number. The second ionization energy is low enough to be recovered from the increased lattice enthalpy (Fig. 14.22). Hence, the Group 2 elements occur with an oxidation number of +2, as the cation M2+, in all their compounds (Table 14.7). Apart from a tendency toward nonmetallic character in beryllium, the elements have all the chemical characteristics of metals, such as having basic oxides and hydroxides. 

The first series is characteristic of a hard acid, the second of a soft acid, and these series appear to be quite general as indicated by the following considerations. For several series of similar ligands, in particular those of elements of the same group of the Menddeef Periodic Table (e. g. F-, C1-, Br and I- RO, RS, RSe and RTe ), the energy Dlx... 

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