Groups IA and IIA

The electron affinities of the group 0 elements are not sufficiently favorable to allow for salt formation even with the most electropositive of these elements, Cs. The electropositive nature of the group-IA and -IIA elements excludes the possibility of bonding such as that discussed in 2.10. 

A large number of compounds of the group IA and IIA metals occur naturally (salt, soda, limestone, etc.). These compounds have been important for thousands of years, and they still are. Moreover, lime is still produced by heating limestone, and the quantity produced is enormous. 

When the oxygen compounds of group IA and IIA metals react with water, strongly basic solutions are produced regardless of whether an oxide, peroxide, or superoxide is involved. 

One preparation of the group IA and IIA sulfides involves the reaction of H2S with the metal hydroxides. 

Because of the tendency of sulfur toward catenation, solutions containing sulfides react with sulfur to give polysulfides, which can be represented as SnJ (see Chapter 15). Sulfides of the group IA and IIA metals can also be produced by reducing the sulfates with carbon at high temperature. 

Most nonmetallic elements will react with the group IA and IIA metals to give binary compounds. Heating the metals with nitrogen or phosphorus gives nitrides and phosphides of the metals. 

Binary carbides are formed when the metals are heated strongly with carbon. The most important carbide of the group IA and IIA metals is calcium carbide, CaC2. Ibis carbide is actually an acelylide because it contains the C/ ion and it reacts with water to produce acetylene. 

Some of the important compounds containing the group IA and IIA metals are the carbonates, nitrates, sulfates, and phosphates. We have already mentioned the mineral trona as the source of sodium carbonate. Calcium carbonate is found in many forms that include chalk, calcite, aragonite, and marble, as well as in egg shells, coral, and seashells. In addition to its use as a building material, calcium phosphate is converted into fertilizers in enormous quantities (see Chapter 14). 

The carbonates, sulfates, nitrates, and phosphates of the group IA and IIA metals are important materials in inorganic chemistry. Some of the most important compounds of the group IA and IIA elements are organometallic compounds, particularly for lithium, sodium, and magnesium, and Chapter 12 will be devoted to this area of chemistry. 

Jolly, W. L. (1972). Metal-Ammonia Solutions. Dowden, Hutchinson Ross, Stroudsburg, PA. A collection of research papers that serves as a valuable resource on all phases of the physical and chemical characteristics of these systems that involve solutions of group IA and IIA metals. 

Most sulhdes (S2 ) are insoluble except those sulfides composed of Group IA and IIA metals or the ammonium ion. 

The Group IA and IIA elements on the activity table will displace hydrogen from water, but not the other metals shown. All the metals above hydrogen will react with acidic solutions to produce hydrogen gas ... 

By reference to the outline periodic table shown on p. (i) we see that the metals and non-metals occupy fairly distinct regions of the table. The metals can be further sub-divided into (a) soft metals, which are easily deformed and commonly used in moulding, for example, aluminium, lead, mercury, (b) the engineering metals, for example iron, manganese and chromium, many of which are transition elements, and (c) the light metals which have low densities and are found in Groups IA and IIA. 

The compounds of lithium and magnesium are the most important of the group IA and IIA organometallics from a synthetic perspective. The metals in these two groups are the most electropositive of the elements. The polarity of the metal-carbon bond is such as to place high electron density on carbon. This electronic distribution is responsible for the strong nucleophilicity and basicity of these compounds. 

In this section, we will discuss organometallic derivatives of zinc, cadmium, mercury, and indium. The group IIB and IIIB metals have the d10 electronic configuration in the 2+ and 3+ oxidation states, respectively. Because of the filled d level, the 2+ or 3+ oxidation states are quite stable, and reactions of the organometallics usually do not involve changes in oxidation level. This property makes the reactivity patterns of these organometallics more similar to those of derivatives of the group IA and IIA metals than to those of derivatives of transition metals with vacancies in the d levels. The IIB metals, however, are... 

Chelation of the main group IA and IIA metal ions in nature is not extensive, an observation attributable to their relatively weak coordination properties and their large hydration energies. However, when it comes to selecting between similar ions, e.g. Na+ and K+, then selective chelation appears to offer the most efficient route. 

Some 20 years ago it was observed that certain antibiotics could induce the movement of aqueous K+ ions into the mitochondria of cells, but not that of aqueous Na+ ions. These antibiotics, many of which are naturally occurring, are termed ionophores, i.e. neutral molecules which can mediate the transport of the essential groups IA and IIA cations across biological membranes.76 The essential features of an ionophore are a highly polar interior, a hydrophobic exterior and conformational flexibility. Many are cyclic peptides, the coordination properties of the cyclic molecules are considerably different to those of the linear peptides. These differences are outlined in Chapter 20.2. 

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