Alkali metals radium

Group 2A—Alkaline earth metals Beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra) are also lustrous, silvery metals, but are less reactive than their neighbors in group 1A. Like the alkali metals, the alkaline earths are never found in nature in the pure state. 

Group 1 elements, beginning with lithium (Li) and running vertically to francium (Fr), are called alkali metals. Group 2 elements, beginning with beryllium (Be) and running vertically to radium (Ra), are called the alkaline earth metals. 

Once again, the periodic table offers clues about which elements could be radioactive naturally. All of the elements in Period 7—like francium in the alkali metals and radium in the alkaline earth metals—are large atoms with many protons. All of the Period 7 elements are radioactive. 

Alkali metals lithium, sodium, potassium, rubidium, cesium, and francium. Metals such as sodium and potassium (the alkali metals) react violently with water—too violently to conduct experiments. The group 2 metals (also called alkaline earth metals) react less readily and can be used in the laboratory. Alkaline earth metals, including beryllium, magnesium, calcium, strontium, barium, and radium. 

Calcium is an alkaline earth metal. The alkaline earth metals make up Group 2 (IIA) of the periodic table, a chart that shows how the elements are related. They also include beryllium, magnesium, strontium, barium, and radium. The alkaline earth metals are more chemically active than most metals. Only the alkali metals in Group I (lA) are more reactive. 

The alkaline earth metals show a wider range of chemical properties than the alkali metals. The IIA metals are not as reactive as the lA metals, but they are much too reactive to occur free in nature. They are obtained by electrolysis of their molten chlorides. Calcium and magnesium are abundant in the earth s crust, especially as carbonates and sulfates. Beryllium, strontium, and barium are less abundant. All known radium isotopes are radioactive and are extremely rare. 

Group 2 of the periodic table contains the alkaline earth metals beryllium, magnesium, calcium, strontium, barium, and radium. These elements are similar to the alkali metals in that they are shiny, ductile, and malleable. The alkaline earth metals have two electrons in their outermost shell. Although they are not as reactive as the alkali metals, the alkaline earth metals are rarely found pure in nature. 

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 common properties of these metals. Radium is not included in the table because all radium isotopes are radioactive and it is difficult and expensive to study the chemistry of this Group 2A element. 

Thus ammonium, NH4, would, if it could be tested, yield two atomic numbers, namely those of hydrogen and nitrogen. Despite its resemblance in combination to an alkali metal, it is not an element. Radium, on the other hand, yields only one atomic number, despite the fact that upon disintegration other elements are obtained from it it is an element, therefore, and not a compound. 

The Group HA elements are called alkaline earfli metals. The alkaline earth metals consist of beiyllium, magnesium, calcium, strontium, baritim, and radium. Their oxides are basic. They have a valence shell configuration of ns, and exhibit an oxidation state of +2. These elements are not as reactive as alkali metals. 

The metals of group 11 of the periodic table —beryllium, magnesium, calcium, strontium, barium, and radium—are called the alkaline-earth metals. Some of their properties are listed in Table 18-2. These metals are much harder and less reactive than the alkali metals because there are twice as many valence electrons. The compounds of all the alkaline-earth metals are similar in composition they all form oxides MO, hydroxides M(0H)2, carbonates MCO3, sulfates MSO4, and other compounds (M = Be, Mg, Ca, Sr, Ba, or Ra). 

C. Remigius Fresenius once again deserves credit for noting, toward the middle of the nineteenth century, that new analytical techniques invariably lead to fresh sets of discoveries. Whereas the element germanium was found on the basis of "classical methods (Clemens Winkler, 1886), Fresenius observation clearly applies to the discovery of the alkali metals rubidium and cesium (by Robert W. Bunsen after he and G. R. Kirch-HOFF first developed emission spectroscopy in 1861). Other relevant examples include the discoveries of radium and polonium (by Madame Curie), hafnium (Hevesy and Coster, 1922), and rhenium (1. Tacke and W. Noddack, 1925), all with the aid of newly introduced X-ray spec-trometric techniques. This is also an appropriate point to mention the discovery of nuclear fission by Otto Hahn and Fritz Strassmann (19. 8), another accomplishment with strongly analytical characteristics 110]. 

The standard reduction potentials, particularly those of the heavier congeners, are similar to those of the heavier alkali metals. These are all good reducing agents. The near-constancy of the E° values of calcium, strontium, barium, and radium reflects a balance of the heats of atomization, ionization, and hydration energies. (See Problem 13.23.) Of course, two electrons must be ionized from the alkaline... 

Radium is the last element in group 2 and is very similar to the other alkali earth metals, which makes it the largest and heaviest element in the group. It particularly resembles barium, which is just above it in group 2 of the periodic table. Radium is a bright white radioactive luminescent alkali earth metal that turns black when exposed to air. Its melting point is 700°C, its boiling point is 1,140°C, and its density is approximately 5.0 g/cm. ... 

Radium, like the other alkali earth metals, readily combines with halogens such as chlorine and bromine (which are electronegative). RaCl and RaBr are the forms in which radium is usually stored and shipped for a variety of uses. 

Radium hydroxide (RaOH) is the most soluble of all the hydroxides of the alkali earth metals. It is formed when radium reacts with water (2Ra + lUjO —> 2RaOH + H T). 

Uranium is a while metal, ductile, malleable, and capable of taking a high polish, but tarnishes readily on exposure to the atmosphere. Finely divided uranium burns upon exposure to air, and the compact metal burns when heated in air at 170 0 Uranium metal slowly decomposes water at ordinary temperatures and rapidly at 100 0 is soluble in HC1 and in HN03 and is nnattacked by alkalis. Chemically related to chromium, molybdenum, and tungsten and, like thorium, is radioactive. In the radioactive decomposition radium is formed. Discovered by Klaproth in 1789. 

Alkaline earth metals are the six elements forming Group Ila in the Periodic Table beryllium (Be), magnesium (Mg), Calcium (Ca), Barium (Ba), Strontium (Sr), and Radium (Ra). Their oxides are basic (alkaline), especially when combined with water. Earth is a historical term applied to nonmetallic substances that are insoluble in water and stable to heating, and also the properties of the oxides. Hence, the term alkali earths is often used to describe these elements. 

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