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Q. Show the Occurrence of the f-block element?
Apart from promethium which is unstable and is found in traces in uranium ores, all the lanthanides usually occur together. Although a large number of minerals are define to contain lanthanides, only three of them, viz., monazite, xenotime and bastnaesite are of commercial importance. Monazite and xenotime are a mixture of phosphates of thorium, lanthanum and lanthanides. Monazite is generally but sparsely distributed in many rocks, but because of its high density and inertness, it is concentrated by weathering into sands on beaches and river beds. Deposits of monazite occur in Southern India, Brazil and South Africa. Bastnaesite is a mixture of fluoride carbonates, LnFC03, of lanthanum and the lanthanides. Both bastnaesite and monazite are richer in the lighter lanthanides, i.e., the cerium earths, but with the difference that monazite also takes upto 30% Thus, which is absent' in bastnaesite. On the other hand xenotime is a valuable source of the heavier rare earths.
Eve known isotope 'of the actinide elements is radioactive and their half-lives are such that only 232, Th235U238 and possibly 244 Pu have survived during the very period of their existence. Only uranium and thorium are found in nature in amounts sufficient for practical extraction. Thorium constitutes 8.1 x 10-4% of the earth's crust and it is almost as abundant as boron. As define earlier, monazite is the most important source of thorium. Uranium comprises 2.3 x 10-4% the earth's crust and it is slightly more abundant than tin. Pitchblende or uraninite, U3O8, and carnotite, K2 (U02)2(V04)2 .3H20, are two important ores uranium.
What is Frenkel defect A pair of one cation and one anion can be missing from an ionic crystal as shown in the following figure. Such a pair of vacant sites is called Schottky
a. How can a colloidal solution and true solution of the similar colour be distinguished from each other? b. Give four applications of adsorption
x(2x^-1/4)^4
what are differences and similarities between covalent bond and electrovalent bond
please give me a complete information about solid and extra information
proton neutron hypothesis
Q. Definition of Avogadros Hypothesis? Ans. Equal volumes of different gases at the same temperature and pressure contain the same number of molecules. At a given temperatu
Physical properties of Dihydric alcohols (a) Dihydric alcohols is a colourless, syrupy liquid and sweet in taste. Its boiling point is 197°C. (b) Dihydric alcohols is misci
What are the distinguishing characteristics of metallic bonding? The metallic state can be imagine as an array of positive ions, with a common pool of electrons to which all th
names of acid redicals of group 1
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