The Alkaline Earth Metals

Sodium bicarbonate is then separated from the solution and heated to give sodium carbonate  

The sodium carbonate obtained this way is dissolved in water, the solittion is filtered to remove the insoluble impurities, and the sodirrm carbonate is crystallized as Na2C03 IOH2O. Finally, the hydrate is heated to give pine, arthydrons sodirrm carborrate. 

The properties of sodium hydroxide and potassirrm hydroxide are very sirrtilar. These hydroxides are prepared by the electrolysis of aqueous NaCl arrd KCl solutions both hydroxides are strong bases and very soluble in water. Sodirrm hydroxide is rrsed in the manrrfacture of soap and many organic and inorganic compounds. Potassium hydroxide is rrsed as an electrolyte in some storage batteries, and aqueous potassium hydroxide is used to remove carbon dioxide and srrlfur dioxide from air. 

Large deposits of sodium nitrate Chile saltpeter) are fotmd in Chile. It decomposes with the evolution of oxygen at about 500°C  

Potassium nitrate (saltpeter) is prepared beginning with the reaction  

The alkaline-earth metals follow the alkali metals in the Periodic Table they are beryllium (Z = 4), magnesium (Z = 12), calcium (Z = 20), strontium (Z — 38), barium (Z = 56), and radium (Z — 88). 

Each of the atoms of the alkaline-earth metals has two valence electrons beyond the same well-shielded nuclei that are present also in the preceding alkali metals. Since the alkaline earths have twice as many valence electrons (which, it will be recalled, hold the atoms together in crystals of the metal) as have the alkali metals, they are harder, more dense, and higher melting than are the alkali metals. Compare, for example, the metals potassium and calcium  

Similar comparisons may be drawn up between other pairs of metals from the two adjacent families. 

The atoms of each of the alkaline-earth metals are smaller than those of the adjacent alkali metals, and the same is true for the ions. The combined effects of decreased size and increased charge make the alkaline-earth ions far better polarizers or distorters than the alkali-metal ions. Their oxides are thus more covalent and their hydroxides less basic than those of the alkali metals. The oxides of beryllium and magnesium are so tightly held together in the solid state that they are quite insoluble in water. 

The reactions of Ca, Sr, and Ba metals with water are less violent than those of the alkali metals beryllium and magnesium metals may survive 

This process is carried out just below 100°C. Because KNO3 is the least soluble salt at room temperature, it is separated from the solution by fractional crystallization. Like NaNOs, KNO3 decomposes when heated. 

Gunpowder consists of potassium nitrate, wood charcoal, and sulfur in the approximate proportions of 6 1 1 by mass. When gunpowder is heated, the reaction is 

The sudden formation of hot expanding gases causes an explosion. 

The alkaline earth metals are somewhat less electropositive and less reactive than the alkali metals. Except for the first member of the family, beryllium, which resembles aluminum (a Group 3A metal) in some respects, the alkaline earth metals have similar chemical properties. Because their ions attain the stable electron configuration of the preceding noble gas, the oxidation number of alkaline earth metals in the combined form is almost always +2. Table 20.5 lists some conunon properties of these metals. Radium is not included in the table because aU radium isotopes are radioactive and it is difficult and expensive to study the chennistry of this Group 2A element. 

The chemistry of magnesium is intermediate between that of beryllium and the heavier Group 2A elements. Magnesium does not react with cold water but does react slowly with steam  

Sodium carbonate (called soda ash) is used in all kinds of industrial processes, including water treatment and the manufacture of soaps, detergents, medicines, and food additives. Today about half of all Na2C03 produced is used in the glass industry. Sodium carbonate ranks eleventh among the chemicals produced in the United States. For many years, Na2C03 was produced by the Solvay process, in which ammonia is first dissolved in a saturated solution of sodium chloride. Bubbling carbon dioxide into the solution precipitates sodium bicarbonate as follows  

However, the rising cost of ammonia and the pollution problem resulting from the by-products have prompted chemists to look for other sources of sodium carbonate. One is the mineral trona [Na5(C03)2(HC03) 2H2O], large deposits of which have been found in Wyoming. When trona is crushed and heated, it decomposes as follows  

The Group 2A(2) elements are called alkaline earth metals because their oxides give basic (alkaline) solutions and melt at such high temperatures that they remained as solids ( earths ) in the alchemists fires. The group includes rare beryllium (Be), common magnesium (Mg) and calcium (Ca), less familiar strontium (Sr) and barium (Ba), and radioactive radium (Ra). The Group 2A(2) Family Portrait presents an overview of these elements. 

Like the alkali metals, the alkahne earth metals are all solids at room temperature and have typical metallic properties ( Table 7.5). Compared with the alkali metals, the alkaline earth metals are harder and denser, and melt at higher temperatures. 

The first ionization energies of the alkahne earth metals are low but not as low as those of the alkali metals. Consequently, the alkahne earth metals are less reactive than their alkah metal neighbors. As noted in Section 7.4, the ease with which the elements lose electrons decreases as we move across a period and increases as we move down a 

Element Electron Configuration Melting Point (°C) Density (g/cm ) Atomic Radius (A) Ii (kj/mol) 

What is the cause of the bubbles that are formed How could you test your answer  

The trend of increasing reactivity within the group is shown by the way the alkaline earth metals behave in the presence of water. BerylHum does not react with either water or steam, even when heated red-hot. Magnesium reacts slowly with liquid water and more readily with steam  

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One current limitation of orbital-free DFT is that since only the total density is calculated, there is no way to identify contributions from electronic states of a certain angular momentum character /. This identification is exploited in non-local pseudopotentials so that electrons of different / character see different potentials, considerably improving the quality of these pseudopotentials. The orbital-free metliods thus are limited to local pseudopotentials, connecting the quality of their results to the quality of tlie available local potentials. Good local pseudopotentials are available for the alkali metals, the alkaline earth metals and aluminium [100. 101] and methods exist for obtaining them for other atoms (see section VI.2 of [97]). 

Group IIB and know that this means the group of elements zine. cadmium and mercury, whilst Group IIA refers to the alkaline earth metals beryllium, magnesium, calcium, barium and strontium. 

The properties of lithium resemble those of the alkaline earth metals rather than those of the alkali metals. Discuss this statement. 

L = lanthanide), are indeed similar to the ions of the alkaline earth metals, except that they are tripositive, not dipositive. 

Spectra of helium and the alkaline earth metal atoms... 

So far we have considered only hydrogen, helium, the alkali metals and the alkaline earth metals but the selection rules and general principles encountered can be extended quite straightforwardly to any other atom. 

Lewis acids, such as the haUde salts of the alkaline-earth metals, Cu(I), Cu(II), 2inc, Fe(III), aluminum, etc, are effective catalysts for this reaction (63). The ammonolysis of polyamides obtained from post-consumer waste has been used to cleave the polymer chain as the first step in a recycle process in which mixtures of nylon-6,6 and nylon-6 can be reconverted to diamine (64). The advantage of this approach Hes in the fact that both the adipamide [628-94-4] and 6-aminohexanoamide can be converted to hexarnethylenediarnine via their respective nitriles in a conventional two-step process in the presence of the diamine formed in the original ammonolysis reaction, thus avoiding a difficult and cosdy separation process. In addition, the mixture of nylon-6,6 and nylon-6 appears to react faster than does either polyamide alone. 

Rubidium metal alloys with the other alkaU metals, the alkaline-earth metals, antimony, bismuth, gold, and mercury. Rubidium forms double haUde salts with antimony, bismuth, cadmium, cobalt, copper, iron, lead, manganese, mercury, nickel, thorium, and 2iac. These complexes are generally water iasoluble and not hygroscopic. The soluble mbidium compounds are acetate, bromide, carbonate, chloride, chromate, fluoride, formate, hydroxide, iodide. 

Sodium—lead alloys that contain other metals, eg, the alkaline-earth metals, are hard even at high temperatures, and are thus suitable as beating metals. Tempered lead, for example, is a beating alloy that contains 1.3 wt % sodium, 0.12 wt % antimony, 0.08 wt % tin, and the remainder lead. The German BahnmetaH, which was used ia axle beatings on railroad engines and cars, contains 0.6 wt % sodium, 0.04 wt % lithium, 0.6 wt % calcium, and the remainder lead, and has a Brinell hardness of 34 (see Bearing MATERIALS). 

BeryUium reacts with fused alkaU haUdes releasing the alkaU metal until an equUibrium is estabUshed. It does not react with fused haUdes of the alkaline-earth metals to release the alkaline-earth metal. Water-insoluble fluoroberyUates, however, are formed in a fused-salt system whenever barium or calcium fluoride is present. BeryUium reduces haUdes of aluminum and heavier elements. Alkaline-earth metals can be used effectively to reduce beryUium from its haUdes, but the use of alkaline-earths other than magnesium [7439-95-4] is economically unattractive because of the formation of water-insoluble fluoroberyUates. Formation of these fluorides precludes efficient recovery of the unreduced beryUium from the reaction products in subsequent processing operations. 

In this section, we will investigate the structure of clusters produced when the metal oven is filled with one of the alkaline earth metals Ca, Sr, or Ba. 

Did we predict the number of atoms required to complete additional layers around the metal-coated C(jo correctly Figure 6 shows a spectrum of Qo covered with the largest amount of Ca experimentally possible (note the logarithmic scale). Aside from the edges of A = 32 and a = 104 which we have already discussed, there are additional clear edges at a = 236 and A = 448 (completion of a third layer was also observed at QoSr23g). Note that these values are identical to the ones just predicted above for the completion of the third and fourth layer of metal atoms. We, therefore, feel confident that the alkaline earth metals studied do, in fact, form the distinct layers around a central C50 molecule with the structures depicted in Fig. 5. 

The structures observed in the mass spectra of fullerene molecules covered with alkaline earth metals, as described in the previous section, all seem to have a geometric origin, resulting in particularly stable cluster configurations every time a highly symmetrical layer of metal atoms around a central fullerene molecule was completed. When replacing the alkaline earth metals by an alkali metal (i.e., Li, Na, K, Rb, or Cs), a quite different situation arises. 

Table 5.1 Atomic properties of the alkaline earth metals...

The carbides of the lanthanoids and actinoids can be prepared by heating M2O3 with C in an electric furnace or by arc-melting compressed pellets of the elements in an inert atmosphere. They contain the C2 unit and have a stoichiometry MC2 or M4(C2)3. MC2 have the CaC2 structure or a related one of lower symmetry in which the C2 units lie at right-angles to the c-axis of an orthogonal NaCl-type cell. They are more reactive than the alkaline-earth metal... 

Arsenites of the alkali metals are very soluble in water, those of the alkaline earth metals less so, and those of the heavy metals are virtually insoluble. Many of the salts are obtained as meta-arsenites, e.g. NaAs02, which comprises polymeric chain anions formed by comer linkage of pyramidal ASO3 groups and held together by Na ions ... 

The product is the dihydrogen orthoperiodate N33H2I06, which is a convenient starting point for many further preparations (see Scheme on next page). Paraperiodates of the alkaline earth metals can be made by the thermal disproportionation of the corresponding iodates, e g. ... 

The three series of elements arising from the filling of the 3d, 4d and 5d shells, and situated in the periodic table following the alkaline earth metals, are commonly described as transition elements , though this term is sometimes also extended to include the lanthanide and actinide (or inner transition) elements. They exhibit a number of characteristic properties which together distinguish them from other groups of elements ... 

Europium and Yb display further similarity with the alkaline earth metals in dissolving in liquid ammonia to give intense blue solutions, characteristic of solvated electrons and presumably also containing [Ln(NH3)x]. The solutions are strongly reducing and decompose on standing with the precipitation of orange Eu(NH2)2 and brown Yb(NH2)2 (always contaminated with Yb(NH2)3) which are isostructural with the Ca and Sr amides. 

Erdalkali, n. alkaline earth, -halogen, n. alkaline-earth halide, -metall, n. alkaline-earth metal, -salze, n.pl. salts of the alkaline-earth metals. 

Electrons are not only charged, they also have a characteristic physicists call spin. Pairing two electrons by spin, which has two possible values, up or down, confers additional stability. Bei yllium (Be, atomic number 4) has two spin-paired electrons in its second shell that are easily given up in chemical reactions. Beryllium shares this characteristic with other elements in column two, the alkaline earth metals. These atoms also generally form ionic bonds. Boron... 

Improved nucleation within the phosphate solution itself can produce smoother coatings without the necessity of recourse to preliminary chemical treatment. This may be accomplished by introducing into the phosphating bath the sparingly soluble phosphates of the alkaline earth metals or condensed phosphates such as sodium hexametaphosphate or sodium tripolyphosphate. Such modified phosphating baths produce smoother coatings than orthodox baths and are very much less sensitive to cleaning procedures. 

The person whose name is most closely associated with the periodic table is Dmitri Mendeleev (1836-1907), a Russian chemist. In writing a textbook of general chemistry, Mendeleev devoted separate chapters to families of elements with similar properties, including the alkali metals, the alkaline earth metals, and the halogens. Reflecting on the properties of these and other elements, he proposed in 1869 a primitive version of today s periodic table. Mendeleev shrewdly left empty spaces in his table for new elements yet to be discovered. Indeed, he predicted detailed properties for three such elements (scandium, gallium, and germanium). By 1886 all of these elements had been discovered and found to have properties very similar to those he had predicted. 

Consider the alkaline earth metal strontium and the transition metal manganese. 

It is therefore possible to determine cations such as Ca2+, Mg2+, Pb2+, and Mn2+ in the presence of the above-mentioned metals by masking with an excess of potassium or sodium cyanide. A small amount of iron may be masked by cyanide if it is first reduced to the iron(II) state by the addition of ascorbic acid. Titanium(IV), iron(III), and aluminium can be masked with triethanolamine mercury with iodide ions and aluminium, iron(III), titanium(lV), and tin(II) with ammonium fluoride (the cations of the alkaline-earth metals yield slightly soluble fluorides). 

With all these advantages one might well wonder why the left-step table has not attracted more attention and indeed why it has not been widely adopted. The answer to this question lies in the placement of one crucial element, helium. In the left-step table, helium is placed among the alkaline earth metals as mentioned above. To most chemists this is completely abhorrent since helium is regarded as the noble gas par excellence. Meanwhile, to a physicist or somebody who emphasizes electronic properties, helium falls rather naturally into the alkaline earths since it has two outer-shell electrons. 

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