Calcium elements-----------——-----------------binary compounds

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. 

In 1817 Dobereiner found that if certain elements were combined with oxygen in binary compounds, a numerical relationship could be discerned among the equivalent weights of these compounds. Thus when oxides of calcium, strontium, and barium were considered, the equivalent weight of strontium oxide was approximately the mean of those of calcium oxide and barium oxide. The three elements in question, strontium, calcium, and barium were said to form a triad. 

The Union of Two Elementary Substances.— The most obvious way in which to prepare a binary compound is by the union of the two constituent elements, though in many cases this is not the most practicable way. Sometimes, the elements are first prepared in pure form and are then combined in other cases, the preparation of the elements and their union is effected in one operation, as in the manufacture of calcium carbide and carborundum. In general, the more dissimilar the two elements the more likely they are to combine readily, but elements of the same general kind sometimes combine with ease, as is the case with chlorine and iodine, sulfur and phosphorus, or sodium and lead. 

The less electronegative element in a binary compound is always named first. Often this element is a metal. You use the same name as the element. For example, sodium chloride, NaCl, calcium oxide, CaO, and zinc sulfide, ZnS, contain the metals sodium, calcium, and zinc. 

Nomenclature of Salts. — Salts containing only two elements follow the rule for binary compounds, aiid hence end in -ide. This suffix is added to an abbreviated form of the name of the non-metal, e.g. chloride, bromide, duor-ide, etc. Notice that the prefix hydro- is omitted, and that the name of the metal precedes, c.g. sodium chloride, potassium bromide, calcium fluoride, etc. It will soon be shown experimentally that salts may be regarded as derived from... 

A substance is considered soluble if more than three grams of the substance dissolves in 100 ml of water. The more common rules are listed below. 1. All common salts of the group 1A elements and ammonium ions are soluble. 2. All common acetates and nitrates are soluble. 3. All binary compounds of group 7A elements (other than F) with metals are soluble except those of silver, mercury(l), and lead. 4. All sulfates are soluble except those of barium, strontium, lead, calcium, silver, and mercury(l). 5. Except for those in Rule 1, carbonates, hydroxides, oxides, sulfides, and phosphates are insoluble. ... 

Remember that in binary compounds containing a metal and a nonmetal, the symbol for the metal is listed first.) The a and b in the formula above represent the subscripts in the empirical formula. For every a atoms of calcium, there are b atoms of phosphorus, or for every a moles of Ca, there are b moles of P. Thus the ratio of to describes the molar ratio of these elements in the compound. 

In these binary compounds the metals take the name of the element, and the anion s name begins with the element but takes the ending -ide. For example, potassium chloride (KCl), aluminum oxide (AI2O3), calcium fluoride (CaF2). 

Oxides can be defined as binary compounds formed between various elements and oxygen, while phosphates can be defined as salts based formally on phosphorus (V) oxoacids and in particular salts of phosphoric (V) acid, H3PO4. Both oxides and phosphates are among the most important classes of inorganic compounds. For example, silicon dioxide (Si02) is the main compound in the Earth s crust, and apatite, a complex mineral form of calcium phosphate, Ca5(P04)3 (OH, F, Cl) is the main compound on the enamel of teeth [1-3],... 

In addition to the types of compounds discussed so far, the group IVA elements also form several other interesting compounds. Silicon has enough nonmetallic character that it reacts with many metals to form binary silicides. Some of these compounds can be considered as alloys of silicon and the metal that result in formulas such as Mo3Si and TiSi2. The presence of Si22 ions is indicated by a Si-Si distance that is virtually identical to that found in the element, which has the diamond structure. Calcium carbide contains the C22-, so it is an acetylide that is analogous to the silicon compounds. 

Ionic compounds consist of positive ions (cations) and negative ions (anions) hence, ionic compounds often consist of a metal and nonmetal. The electrostatic attraction between a cation and anion results in an ionic bond that results in compound formation. Binary ionic compounds form from two elements. Sodium chloride (NaCl) and sodium fluoride (NaF) are examples of binary ionic compounds. Three elements can form ternary ionic compounds. Ternary compounds result when polyatomic ions such as carbonate (C032 ), hydroxide (OH-), ammonium (NH4+), form compounds. For example, a calcium ion, Ca2+, combines with the carbonate ion to form the ternary ionic compound calcium carbonate, CaC03. Molecular compounds form discrete molecular units and often consist of a combination of two nonmetals. Compounds such as water (H20), carbon dioxide (C02), and nitric oxide (NO) represent simple binary molecular compounds. Ternary molecular compounds contain three elements. Glucose ( 12 ) is a ternary molecular compound. There are several distinct differences between ionic and molecular compounds, as summarized in Table 1.2. 

CARBIDES. A binary solid compound of carbon and another element. The most familiar carbides are those of calcium, tungsten, silicon, boron, and iron (cemcntitc) Two factors have an important bearing on the properties of carbides (1) the difference in electronegativity between carbon and the second elemenl. and (2) whether the second element is a transition metal. Saltlike carbides of alkali metals are obtained by reaction with acetylene. Those ohlained from silver, copper, and mercury sails are explosive. See also Carbon and Iron Metals, Alloys, and Steels. 

The term HYDRIDE is used in two ways. It is the generic name for all binary hydrogen compounds, and the specific name for the binary hydrogen compounds of the group IR and 2R elements, for example, lithium hydride and calcium hydride. 

For some elements such as calcium (Ca) and a number of rare earth elements (REE) their suitability in binary Mg alloys has already been proven. But further work still needs to be undertaken to assure that the intermetallic compound of Mg-Ca and Mg-REE are also not harmful to the human body. In the case that ternary or even more complex alloys will be developed the same tests have to be applied to make sme that all compounds that may form are safe. The experimental work in this area has to be accompanied by thermodynamic calculations. While binary phase diagrams are available for most elemental combinations, there are also reliable phase diagrams for a number of ternary systems. A major challenge is still the calculation of phase formation in more complex systems. Moreover, it might be the case that Mg alloy systems which contain more than three alloy components will be better solutions for biodegradable implants than those ones which are actually presented in literature. 

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