Alkaline earths Group elements

Group-2 Elements Alkaline Earth Metals Increasing Decreasing Exceptions... 

Symbol Ba atomic number 56 atomic weight 137.327 a Group llA (Group 2) alkaline earth element electronic configuration [Xejs valence state +2 ionic radius of Ba2+ in crystal (corresponding to coordination number 8) 1.42 A first ionization potential lO.OOeV stable isotopes and their percent abundances Ba-138 (71.70), Ba-137 (11.23), Ba-136 (7.85), Ba-135 (6.59), Ba-134 (2.42) minor isotopes Ba-130 (0.106) and Ba-132 (0.101) also twenty-two radioisotopes are known. 

Symbol Ca atomic number 20 atomic weight 40.078 a Group IIA (Group 2) alkaline-earth metaUic element ionic radius 1.06 A (Ca2+) electron configuration [Ar]4s2 valence state +2 standard electrode potential, E° = -2.87V stable isotopes and their abundance Ca-40 (97.00%), Ca-44 (2.06%) Ca-42 (0.64%), Ca-48 (0.18%), Ca-43 (0.145%), and Ca-46 (0.003%) also the element has six unstable isotopes of which Ca-41 has the longest half-life, l.lxlO yr (decay mode electron capture), and Ca-38 has shortest half life 0.66 sec (P-decay). 

RADIUM. [CAS 7440-14-41, Chemical element symbol Ra, at. no. 88, at. wt. 226.025, periodic table group 2 (alkaline earths), mp 700VC, bp 1,140°C, density 5 g/cm3 (20°C). Radium metal is white, rapidly oxidized in air, decomposes H O, and evolves heat continuously at the rate of approximately 0.132 calorie per hour per mg when the decomposition products are retained, and the temperature of radium salts remains about 1,5°C above the surrounding environment. Radium is formed by radioactive transformation of uranium, about 3 million parts of uranium being accompanied in nature by 1 part radium. Radium spontaneously generates radon gas at approximately the rate of 100 mmJ per day per gram of radium, at standard conditions, Radium usually is handled as the chloride or bromide, either as solid or in solution. The radioactivity of the material... 

The presence of radium in biological materials or environmental samples is generally determined by virtue of its radioactivity. Except in the laboratory where radium compounds have been isolated and determined for a certain purpose, determination of radium compounds in biological and environmental samples is relatively rare. As a Group IIA alkaline earth element, radium is similar in its chemical behavior to other members of that group, especially its nearest neighbor, barium. For example, radium tends to precipitate as the sulfate, which is the basis for its isolation for chemical analysis by coprecipitation with barium sulfate. Furthermore, radium associates with calcium in living systems and accumulates in bone. The determination of radium compounds or specific isotopes is usually accomplished by a separation procedure, followed by quantitative analysis of total radium based on its radioactivity. 

Elements in both groups are highly reactive and share many characteristics. In this chapter, we describe the Group 1 alkali metals and the Group 2 alkaline earth metals. Specifically, we cover how they react to form various ions and compounds and where you are likely to encounter them. 

The hypothesis got some support fi-om the fact that the activity coprecipitated from the solution of irradiated uranium with a precipitate of salts of added barium — the lighter homologue of radium. Hahn and coworkers used a coprecipitation with barium chloride from a solution of concentrated hydrochloric acid. Under these conditions, the BaCl2 precipitate is very clean and one could conclude that a radioactive species coprecipitated would have to be an element belonging to the group of alkaline earths, namely Sr, Ba, or Ra. Since barium... 

Metals alkali metals (group 1 elements), alkaline earth metals (group 2 elements), transition metals (groups 3 to 11), post-transition metals (group 12 elements and Al, Ga, In, Tl, Sn, Pb, Bi), lanthanides and actinides... 

Look now at the configurations of beryllium, magnesium, and calcium, members of the group of alkaline earth metals (Group IIA), which are similar, moderately reactive elements. 

In the periodic table, the/block elements are wedged between Groups 3 and 4 in the sixth and seventh periods. The position of these inner transition elements reflects the fact that they involve the filling of the 4/ sublevel. With seven 4/orbitals to be filled with two electrons each, there are a total of 14/-block elements between lanthanum. La, and hafnium, Hf, in the sixth period. The lanthanides are shiny metals similar in reactivity to the Group 2 alkaline-earth metals. 

Figure 7.15 shows samples of the Group 2A elements. As a group, the alkaline earth metals are somewhat less reactive than the alkali metals. Both the first and the second ionization eneigies decrease (and metallic character increases) from beryllium to barium. Group 2A elements tend to form M ions, where M denotes an alkaline earth metal atom. 

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. 

These elements form two groups, often called the alkali (Group I) and alkaline earth (Group II) metals. Some of the physical properties usually associated with metals—hardness, high m.p. and b.p.—are noticeably lacking in these metals, but they all have a metallic appearance and are good electrical conductors. Table 6.1 gives some of the physical properties. 

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