Calcium elements

Product (% Elemental Calcium) Elemental Calcium per Tablet (mg) Vitamin D per Tablet (IU)... 

Product ( /o calcium)" Elemental Calcium (mg) Vitamin D (units)... 

The number of chemical elements has now reached 109, and the list is growing. Fortunately for students, only about 40 are relevant to basic chemistry. Please take a reconnaissance glance at the periodic table of chemical elements (found at the end of this chapter) and find calcium, element number 20. You need to be acquainted with the symbol and general properties of the 20 simplest elements up to calcium, plus another 20 of chemical significance that you will encounter in this book. 

The Caabundance has been studied in stars by optical spectra. Because 40 Ca dominates the spectra of Ca in stars, and especially because 4°Ca is a primary alpha nucleus, the galactic evolution of 4°Ca is the same as the observed galactic evolution of calcium elemental abundance. As nucleosynthesis progressed in the galaxy the Ca/H abundance... 

In the attempt to synthesize molecular sieves with isomorphous substitutions of A1 and/or Si by the divalent calcium element in the tetrahedral positions, we obtained a new calcium silicate phase by inclusion of heteroatom calcium into silicate sols. The characterization results showed that as-synthesized calcium silicate, named CAS-1 (Calcium silicate No. 1), was a novel zeolite-like crystal material with the cation reversibly exchangeable and selectively adsorptive properties. In this paper, the effects of composition of raw materials, reaction temperature and the different alkali ion on the hydrothermal synthesis of calcosilicate crystal material CAS-1 were investigated and the uptake of different cation on the thermal stability of CAS-1 structure was also examined. The sample was characterized by XRD, TEM, SEM, DT-TGA, BET, AAS and chemical analysis. 

Mendeleev was convinced that he had discovered what he called the Periodic Law. The principle of the law was that the characteristics of the elements would vary periodically (that is, repeat at set intervals) as atomic weight went up. Characteristics such as specific density, oxidation states, and affinity (degree of chemical interactions) would vary for each element, but such variation was within a specific range that was common to a particular group. Thus, calcium (element 20) might be much heavier than magnesium (element 12) and only a bit heavier than potassium (element 19), but calcium and magnesium were related by chemical behavior. 

Calcium, element number 20, is a silvery-gray metal with a density of 1.55 g/cm3. The main source of calcium is seawater. Sedimentary materials that contain calcium include calcite, limestone, marble, and chalk (all of which are forms of calcium carbonate, CaC03), gypsum (CaS04 x 2H20), and dolomite (CaMg(C03)2). 

Table 35.8. Percent of Elemental Calcium Content in Various Salts (3) Salt Calcium (%)Elemental Calcium (mg/tablet)...

In the periodic table, calcium, element 20, is surrounded by elements 12, 19, 21, and 38. Which of these have ph) ical and chemical properties most resembling calcium ... 

The usual way to avoid this interference is to prevent the formation of calcium phosphate during the desolvation of the sample solution in the burner. This can be done by adding another element in excess which binds the phosphate more strongly than calcium. Elements such as strontium, barium, and landianum have been used successfully for that purpose. The other possibility is to add a complexing agent such as EDTA, which forms a complex with calcium and hence prevents the analyte element from reacting with phosphate. 

X-ray fluorescence A method of analysis used to identify and measure heavy elements in the presence of each other in any matrix. The sample is irradiated with a beam of primary X-rays of greater energy than the characteristic X-radiation of the elements in the sample. This results in the excitation of the heavy elements present and the emission of characteristic X-ray energies, which can be separated into individual wavelengths and measured. The technique is not suitable for use with elements of lower atomic number than calcium. 

The FCC structure is illustrated in figure Al.3.2. Metallic elements such as calcium, nickel, and copper fonu in the FCC structure, as well as some of the inert gases. The conventional unit cell of the FCC structure is cubic with the lengdi of the edge given by the lattice parameter, a. There are four atoms in the conventional cell. In the primitive unit cell, there is only one atom. This atom coincides with the lattice pomts. The lattice vectors for the primitive cell are given by... 

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 white solid oxides MjO and M 0 are formed by direct union of the elements. The oxides MjO and the oxides M"0 of calcium down to radium have ionic lattices and are all highly basic they react exothermically with water to give the hydroxides, with acids to give salts, and with carbon dioxide to give carbonates. For example... 

The elements in Group II of the Periodic Table (alkaline earth metals) are. in alphabetical order, barium (Ba). beryllium (Be), calcium (Ca). magnesium (Mg), radium (Ra) and strontium (Sr). 

Never found free in nature, it is widely distributed in combination with minerals. Phosphate rock, which contains the mineral apatite, an impure tri-calcium phosphate, is an important source of the element. Large deposits are found in Russia, in Morocco, and in Florida, Tennessee, Utah, Idaho, and elsewhere. 

Calcium is a metallic element, fifth in abundance in the earth s crust, of which if forms more than 3%. It is an essential constituent of leaves, bones, teeth, and shells. Never found in nature uncombined, it occurs abundantly as limestone, gypsum, and fluorite. Apatite is the fluorophosphate or chlorophosphate of calcium. 

Mixed with sand it hardens as mortar and plaster by taking up carbon dioxide from the air. Calcium from limestone is an important element in Portland cement. 

It is recovered commercially from monazite sand, which contains about 3%, and from bastnasite, which contains about 0.2%. Wohler obtained the impure element in 1828 by reduction of the anhydrous chloride with potassium. The metal is now produced commercially by reduction of the fluoride with calcium metal. It can also be prepared by other techniques. 

Rubidium can be liquid at room temperature. It is a soft, silvery-white metallic element of the alkali group and is the second most electropositive and alkaline element. It ignites spontaneously in air and reacts violently in water, setting fire to the liberated hydrogen. As with other alkali metals, it forms amalgams with mercury and it alloys with gold, cesium, sodium, and potassium. It colors a flame yellowish violet. Rubidium metal can be prepared by reducing rubidium chloride with calcium, and by a number of other methods. It must be kept under a dry mineral oil or in a vacuum or inert atmosphere. 

Barium is a metallic element, soft, and when pure is silvery white like lead it belongs to the alkaline earth group, resembling calcium chemically. The metal oxidizes very easily and should be kept under petroleum or other suitable oxygen-free liquids to exclude air. It is decomposed by water or alcohol. 

The element may be obtained by separating neodymium salts from other rare earths by ion-exchange or solvent extraction techniques, and by reducing anhydrous halides such as NdFs with calcium metal. Other separation techniques are possible. 

Terbium has been isolated only in recent years with the development of ion-exchange techniques for separating the rare-earth elements. As with other rare earths, it can be produced by reducing the anhydrous chloride or fluoride with calcium metal in a tantalum crucible. Calcium and tantalum impurities can be removed by vacuum remelting. Other methods of isolation are possible. 

L. Holmia, for Stockholm). The special absorption bands of holmium were noticed in 1878 by the Swiss chemists Delafontaine and Soret, who announced the existence of an "Element X." Cleve, of Sweden, later independently discovered the element while working on erbia earth. The element is named after cleve s native city. Holmia, the yellow oxide, was prepared by Homberg in 1911. Holmium occurs in gadolinite, monazite, and in other rare-earth minerals. It is commercially obtained from monazite, occurring in that mineral to the extent of about 0.05%. It has been isolated by the reduction of its anhydrous chloride or fluoride with calcium metal. 

The Elements Beryllium (Be), Magnesium (Mg), and Calcium (Ca) all formed oxides in fhe ratio of one afom per oxygen atom RO Boron (B) and Aluminum (Al) formed R2O3 Carbon (C) and Silicon (Si) formed RO2... 

Acetylene was discovered m 1836 by Edmund Davy and characterized by the French chemist P E M Berthelot m 1862 It did not command much attention until its large scale preparation from calcium carbide m the last decade of the nineteenth century stim ulated interest m industrial applications In the first stage of that synthesis limestone and coke a material rich m elemental carbon obtained from coal are heated m an electric furnace to form calcium carbide... 

For binary compounds the name of the element standing later in the sequence in Sec. 3.1.1.3 is modified to end in -ide. Elements other than those in the sequence of Sec. 3.1.1.3 are taken in the reverse order of the following sequence, and the name of the element occurring last is modified to end in -ide e.g., calcium stannide. 

Minimizing Chemical Interferences The quantitative analysis of some elements is complicated by chemical interferences occurring during atomization. The two most common chemical interferences are the formation of nonvolatile compounds containing the analyte and ionization of the analyte. One example of a chemical interference due to the formation of nonvolatile compounds is observed when P04 or AP+ is added to solutions of Ca +. In one study, for example, adding 100 ppm AP+ to a solution of 5 ppm Ca + decreased the calcium ion s absorbance from 0.50 to 0.14, whereas adding 500 ppm POp to a similar solution of Ca + decreased the absorbance from 0.50 to 0.38. These interferences were attributed to the formation of refractory particles of Ca3(P04)2 and an Al-Ca-O oxide. 

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