Sodium elemental properties

To which class of elements do lithium, sodium, and potassium belong What are their elemental properties ... 

Strontium [7440-24-6] Sr, is in Group 2 (IIA) of the Periodic Table, between calcium and barium. These three elements are called alkaline-earth metals because the chemical properties of the oxides fall between the hydroxides of alkaU metals, ie, sodium and potassium, and the oxides of earth metals, ie, magnesium, aluminum, and iron. Strontium was identified in the 1790s (1). The metal was first produced in 1808 in the form of a mercury amalgam. A few grams of the metal was produced in 1860—1861 by electrolysis of strontium chloride [10476-85-4]. 

The seventh element in order of abundance in the Earth s crust is potassium - about the same as sfjdium with similar properties. While sodium is readily available from the ocean, potassium is found and extracted from many mineral formations. About 90 percent of the potassium that is extracted goes to the production of fertilizers. Other purposes for it are ceramics and fire extinguishers for which potassium bicarbonate is better than sodium bicarbonate. 

The alkali metals form a homogeneous group of extremely reactive elements which illustrate well the similarities and trends to be expected from the periodic classification, as discussed in Chapter 2. Their physical and chemical properties are readily interpreted in terms of their simple electronic configuration, ns, and for this reason they have been extensively studied by the full range of experimental and theoretical techniques. Compounds of sodium and potassium have been known from ancient times and both elements are essential for animal life. They are also major items of trade, commerce and chemical industry. Lithium was first recognized as a separate element at the beginning of the nineteenth eentury but did not assume major industrial importance until about 40 y ago. Rubidium and caesium are of considerable academic interest but so far have few industrial applications. Francium, the elusive element 87, has only fleeting existence in nature due to its very short radioactive half-life, and this delayed its discovery until 1939. 

The Group 1 elements are soft, low-melting metals which crystallize with bee lattices. All are silvery-white except caesium which is golden yellow "- in fact, caesium is one of only three metallic elements which are intensely coloured, the other two being copper and gold (see also pp. 112, 1177, 1232). Lithium is harder than sodium but softer than lead. Atomic properties are summarized in Table 4.1 and general physical properties are in Table 4.2. Further physical properties of the alkali metals, together with a review of the chemical properties and industrial applications of the metals in the molten state are in ref. 11. 

The properties of compounds are very different from those of the elements they contain. Ordinary table salt, sodium chloride, is a white, unreactive solid. As you can guess from its name, it contains the two elements sodium and chlorine. Sodium (Na) is a shiny, extremely reactive metal. Chlorine (Cl) is a poisonous, greenish-yellow gas. Clearly, when these two elements combine to form sodium chloride, a profound change takes place (Figure 1.3, page 4). 

Table 6-VI11 presents some properties of the elements we are considering. The first three, sodium, magnesium, and aluminum, are metallic. The melting points and boiling points are high and increase as we go from element to element. This trend reflects stronger and stronger bonding and it is paralleled by a decrease in the atomic volume.

Sodium hydroxide, NaOH, when dissolved in water, gives a solution with the properties of a base. The hydroxides of many elements—those from the left side of the periodic table—behave in the same way. Perhaps they dissolve to form ions of the sort... 

But there is a second notion, which Mendeleev sometimes called "real dements," in order to indicate their more fundamental status. In Bis sense, Ihe eh emants represent abstract substances that lack what wc normally regard as properties and that represent the form that elements take when they occur in compounds. For example, sodium and chlorine as simple substances—a grey mrt.il and a gicmish gas respectively—are nol literally present in the compound sodium chloride (table salt). Mendeleev would have said Brat sodium and chlorine are present In the compound as the abstract or "real ctemanls. ... 

There is convincing experimental evidence for the following important statement. To a degree of approximation satisfactory for most analytical work, the mass absorption coefficient of an element is independent of chemical or physical state. This means, for example, that an atom of bromine has the same chance of absorbing an x-ray quantum incident upon it in bromine vapor, completely or partially dissociated in potassium bromide or sodium bromate in liquid or solid bromine. X-ray absorption is predominantly an atomic property. This simplicity is without parallel in absorptiometry. 

The members of Group 1 are called the alkali metals. The chemical properties of these elements are unique and strikingly similar from one to another. Nevertheless, there are differences, and the subtlety of some of these differences is the basis of the most subtle property of matter consciousness. Our thinking, which relies on the transmission of signals along neurons, is achieved by the concerted action of sodium and potassium ions and their carefully regulated migration across membranes. So, even to learn about sodium and potassium, we have to make use of them in our brains. 

Beryllium, at the head of Group 2, resembles its diagonal neighbor aluminum in its chemical properties. It is the least metallic element of the group, and many of its compounds have properties commonly attributed to covalent bonding. Beryllium is amphoteric and reacts with both acids and alkalis. Like aluminum, beryllium reacts with water in the presence of sodium hydroxide the products are the beryl-late ion, Be(OH)42, and hydrogen ... 

One early attempt to organize the elements clustered them into groups of three, called triads, whose members display similar chemical properties. Lithium, sodium, and potassium, for example, have many common properties and were considered to be a triad. This model was severely limited, for many elements could not be grouped into triads. The triad model is just one of nearly 150 different periodic arrangements of the elements that have been proposed. 

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