Alkaline earth metals radioactive isotopes

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. 

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. 

There are four stable isotopes of strontium that are found naturally. In addition there are about twenty radioactive isotopes, including strontium-90, a deadly by-product of nuclear-bomb detonations. The natural forms of strontium are relatively nontoxic. Similar to calcium both physically and chemically, elemental strontium is a soft, shiny metal. Like calcium and other alkaline earth metals, it is easily oxidized and thus not found naturally in its free elemental state. Instead, it almost always is found in the + 2 oxidation state, forming such compounds as strontium oxide (SrO), strontium sulfate (SrS04, from the mineral celestite), strontium carbonate (SrCOj, from the mineral strontianite), and strontium chloride (SrC. Strontium nitrate, Sr(N03)2, is used to produce the brilliant red color seen in some fireworks and signal flares and is also used in making tracer bullets that can be seen when fired at night. Other strontium compounds are sometimes used in the manufacture of special glasses. Yet overall, strontium is not a very important element industrially or commercially, see ALSO Davy, Humphry... 

Rubidium The stable isotopes Rb and Rb were determined by direct ICP-MS measurements. It should be pointed out that the original intention was to isolate the individual alkali and alkaline earth metals by using cation and ion-exchange columns. The radioactive rubidium and barium isotopes had, however, decayed before dissolution of the samples and therefore only stable isotopes of these elements were determined (by ICP-MS), with the exception of °Sr, Cs, and Cs. 

The heaviest member of the alkaline earth metals is radium (Ra), a naturally radioactive element discovered by Pierre and Marie Cnrie in 1898. Radinm was initially isolated from the nraninm ore pitchblende, in which it is present as approximately 1.0 g per 7.0 metric tons of pitchblende. How many atoms of radinm can be isolated from 1.75 X 10 g pitchblende (1 metric ton = 1000 kg) One of the early uses of radium was as an additive to paint so that watch dials coated with this paint wonld glow in the dark. The longest-lived isotope of radinm has a half-life of 1.60 X 10 years. If an antique watch, manufactured in 1925, contains 15.0 mg radinm, how many atoms of radinm will remain in 2025 ... 

Strontium is an alkaline earth element in Group IIA of the periodic table. Because of its high reactivity, elemental (or metallic) strontium is not found in nature it exists only as molecular compounds with other elements. The chemical information for elemental strontium and some of its compounds is listed in Table 4-1. Radioactive isotopes of strontium (e g., 89Sr and 90Sr, see Section 4.2) are the primary cause of concern with regard to human health (see Chapter 3). 

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