Binary compound, meaning

For optoelectronics the binary compound semiconductors drawn from Groups 13 and 15 (III and V) of the Periodic Table are essential. These often have direct rather than indirect band gaps, which means that, unlike Si and Ge, the lowest lying absorption levels interact strongly with light. The basic devices of... 

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 formulas of ionic compounds have a different meaning from those of molecular compounds. Each crystal of sodium chloride has a different total number of cations and anions. We cannot simply specify the numbers of ions present as the formula of this ionic compound, because each crystal would have a different formula and the subscripts would be enormous numbers. However, the ratio of the number of cations to the number of anions is the same in all the crystals, and the chemical formula shows this ratio. In sodium chloride, there is one Na+ ion for each Cl ion so its formula is NaCl. Sodium chloride is an example of a binary ionic compound, a compound formed from the ions of two elements. Another binary compound, CaCl2, is formed from Ca2+ and Cl- ions in the ratio 1 2, which is required for electrical neutrality. 

The symbols suggested by Jensen, based on Niggli s proposals, describe the local coordination by means of coordination number ratios. For instance, a formula AEm/n will indicate a binary compound where m is the coordination number (defined as the nearest-neighbour number (NNN)) of atoms E around A and n is the similarly defined coordination number of A around E. 

Compounds made by insertion at room temperature are often metastable - if heated, they change their structure or decompose into other compounds. That does not rule out using thermodynamics it just means that processes happening slowly compared to the duration of an experiment are assumed to be frozen. At room temperature, the ratio of Mo to Se in a host like Mo Seg is fixed. From the point of view of thermodynamics, the constraint that the host remain Mo Seg means that we can regard an intercalation compound like Li -MogSeg as a pseudo-binary compound instead of a ternary one. 

Many binary compounds (those with only 2 elements) contain more than 1 cation or anion. The general binary compound can be written CW, in which the subscripts mean the compound has x cations and y anions. In this case, the solubility equation is... 

One informative means of organizing a discussion of binary alkah metal compounds is by group in the periodic table. The overview provided below begins with binary alloys formed with other alkali metals and ends with binary compounds formed with halogens. The focus is primarily on second row elements. More detailed discussions can be found in the books concerning inorganic chemistry [26, 27]. 

Ionic crystals are compounds by necessity. Let us regard a binary compound (A[ X) and derive the electronic conductivity (transference) as a function of its component activity. From Eqn. (4.84) and the necessarily prevailing ionic defects, we can conclude that the ionic conductivity is independent of the component activities which, however, does not mean that the total conductivity is also constant. Let us first formulate the equilibrium between crystal A, X and component X2... 

Let us now turn to cross effects proper between electronic and ionic fluxes. Considering the general nature of cross effects in crystals, our analysis will be performed in some depth. It gives us the tools for a correct application of SE transport theory (see Section 4.2.2) and explains to some extent the physical meaning of the cross coefficients. Let us illustrate the problem using a semiconducting binary compound such as a transition-metal oxide. In A, 0 crystals with the B1 structure, oxygen... 

An inorganic compound means, in general, a compound that does nol contain carbon atoms. Some very simple carbon compounds, such as carbon monoxide and dioxide, binary metallic carbon compounds (carbides) and carbonates, arc also included in the group of inorganic compounds. 

Here we consider the factors which determine whether a given compound prefers an ionic structure or a covalent one. We may imagine that for any binary compound - e.g. a halide or an oxide - either an ionic or a covalent structure can be envisaged, and these alternatives are in thermochemical competition. Bear in mind that there may be appreciable covalency in ionic substances, and that there may be some ionic contribution to the bonding in covalent substances. Since there is no simple means - short of a rigorous MO treatment - of calculating covalent bond energies, and since quantitative calculations based upon the ionic model are subject to some uncertainties, the question of whether an ionic or a covalent structure is the more favourable thermodynamically cannot be answered in absolute terms. We can, however, rationalise the situation to some extent. 

The most obvious route to a binary compound ExE y is the direct interaction between the elemental substances E and E. This is often precluded by thermodynamic considerations however, a great many compounds that are unstable with respect to the elemental substances are kinetically stable and can be prepared by other means. Even if the reaction between the elemental substances is possible, both from thermodynamic and kinetic viewpoints, an indirect synthesis may be preferable for practical reasons. We shall illustrate these principles by looking at some examples of synthetic routes to binary hydrides and halides. 

Evidently, in the course of layer formation the plane of inert markers cannot coincide with the initial interface between substances A and B. It would mean that compound layers could grow at the expense of one component. Chemically, this is impossible since any binary compound consists of two components. Position of the layers relative to the initial interface is mainly dependent upon the stoichiometry of chemical compounds, if both ends of a couple are equally free to move. Coincidence of initial and marker planes provides evidence for the lack of contact between reacting phases at that place. 

The phenomenon of superconductivity is common in several particular types of compounds. Thus more than two dozen binary compounds with the fee sodium chloride (NaCl) stracture are superconducting. The carbides AC and nitrides AN, such as NbN with Tc = 17 K, have the highest transition temperatures of this group, and the metallic A atoms with values above 10 K were Nb, Mo, Ta, W, and Zr. The NaCl-type superconductors are compositionally stoichiometric but not structurally so. hi other words, these compounds have a small to moderate concentration of vacancies in the lattice. For example, YS has 10% vacancies, which means that its chemical formula should properly be written 0,980.9. Nonstoichiometric NaCl-type compounds such as Tai.oCo.ye also exist. Ordinarily the vacancies are random, but sometimes they are ordered. 

The strength of the triple bond in the N2 molecule is important both thermodynamically and kinetically. Thermodynamically, the great stability of the N=N bond means that most binary compounds containing nitrogen decompose exothermically to the elements, for example ... 

The atomic and ionic properties of an element, particularly IE, ionic radius and electronegativity, underly its chemical behaviour and determine the types of compound it can form. The simplest type of compound an element can form is a binary compound, one in which it is combined with only one other element. The transition elements form binary compounds with a wide variety of non-metals, and the stoichiometries of these compounds will depend upon the thermodynamics of the compound-forming process. Binary oxides, fluorides and chlorides of the transition elements reveal the oxidation states available to them and, to some extent, reflect trends in IE values. However, the lEs of the transition elements are by no means the only contributors to the thermodynamics of compound formation. Other factors such as lattice enthalpy and the extent of covalency in bonding are important. In this chapter some examples of binary transition element compounds will be used to reveal the factors which determine the stoichiometry of compounds. 

There is a lot of oxygen in the atmosphere, and over the millions of years since the Earth was formed many metals have combined with oxygen to form compounds called oxides. Iron, for example, occurs in the molten core of our Earth, and is often found in the Earth s crust as the ore haematite, which is iron oxide. Iron oxide is a binary compound, which means it contains only two elements. Notice that its name ends with ide . This is true for all binary compounds. Metals tend to combine with non-metals. Where a binary compound is made up of a metal and a non-metal, the first name of the compound is simply the name of the metal it contains and the second is the name of the non-metal, changed to end in ide for example, the compound between copper and chlorine is copper chloride. 

Hundreds of compounds contain ionic bonds. Many ionic compounds are binary, which means that they contain only two different elements. Binary ionic compounds contain a metallic cation and a nonmetallic anion. Magnesium oxide, MgO, is a binary compound because it contains the two different elements magnesium and oxygen. However, CaS04 is not a binary compound. Can you explain why ... 

Binary means two. Binary compounds contain two elements. 

Some compounds contain polyatomic ions that behave much like monatomic anions. Compounds that contain these ions are called pseudobinary ionic compounds. The prefix pseudo- means false these compounds are named as though they were binary compounds. The common examples of such polyatomic anions are the hydroxide ion, OH , and the cyanide ion, CN. The ammonium ion, NH4+, is the common cation that behaves like a simple metal cation. 

The chemistry required to convert the oxide to other binary compounds is independent of the scale of operation. However, with microscale synthetic methods applied to radioactive materials, successful preparations are achieved more readily by carrying out the chemistry in situ, that is, in such a manner that eliminates, or at least minimizes, the necessity of having to "handle" the sample during or following its synthesis. Thus, actinide compounds are usually prepared in silica capillary tubes which can be flame sealed at the conclusion of a synthesis to provide the desired sample for study in a small volume, quartz container. A special feature of the preparation/vacuum system in the TRL is the capability to interrupt a synthesis, isolate (by means of a stopcock) and remove the sample, examine it in... 

Several NaCl-type binary compounds, including UN, have been analyzed (14) using both theoretical band structure (itinerant) and crystal field (localized) approaches (although the applicability of one of these approaches generally means that the other is inappropriate). UN may be an intermediate case where neither approach will yield very satisfactory results. Photoemission spectroscopy can yield valuable insights into this problem. 

Ternary compounds differ from pseudo-binary compounds in that the different crystallographic sites are occupied by different types of atoms. In general, one might say that the physical properties of pseudo-binaries can be described by a weighted mean of the properties of the parent binary compounds from which they are derived. This is no longer true for ternary compounds. Here one may expect novel properties not found in binary compounds. Very often also the crystal structure and the formula composition have no analogue in the corresponding binary systems. Up to now, systematic experimental studies as to the occurrence of ternary compounds... 

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