Ionic bond definition

For a given molecule and a given intemuclear separation a would have a definite value, such as to make the energy level for P+ lie as low as possible. If a happens to be nearly 1 for the equilibrium state of the molecule, it would be convenient to say that the bond is an electron-pair bond if a is nearly zero, it could be called an ionic bond. This definition is somewhat unsatisfactory in that it does not depend on easily observable quantities. For example, a compound which is ionic by the above definition might dissociate adiabatically into neutral atoms, the value of a changing from nearly zero to unity as the nuclei separate, and it would do this in case the electron affinity of X were less than the ionization potential of M. HF is an example of such a compound. There is evidence, given bdow, that the normal molecule approximates an ionic compound yet it would dissociate adiabatically into neutral F and H.13... 

In other cases, discussed below, the lowest electron-pair-bond structure and the lowest ionic-bond structure do not have the same multiplicity, so that (when the interaction of electron spin and orbital motion is neglected) these two states cannot be combined, and a knowledge of the multiplicity of the normal state of the molecule or complex ion permits a definite statement as to the bond type to be made. 

Am. SC I2 and (NH4),S involve covalent bonding, and therefore by definition, electron sharing. (NH4KS also exhibits ionic bonding. 

The possible formation of a dipole is a feature of covalent bonding but it is obvious that an ionic bond results in a definite unequal distribution of electrons within a molecule and such molecules (or ions) are extremely polar. However, the fact that they carry a definite charge enables additional separation techniques to be applied. The rate of migration in an electric field (electrophoresis) and the affinity for ions of opposite charge (ion-exchange chromatography) are extremely valuable techniques in the separation of ionic species. 

Both cationic adsorption and anionic adsorption belong to what is called ionic adsorption. Covalent adsorption is due to the localized covalent bonding, and metallic adsorption is due to the delocalized covalent bonding. The distinction among these three modes of chemisorption, however, is not so definite that the transition from the covalent through the metallic to the ionic adsorption may not be discontinuous, but rather continuous, in the same way as the transition of the three-dimensional solid compounds between the covalent, metallic, and ionic bonding. 

Pauling offered the following definition of a chemical bond ... there is a chemical bond between two atoms or groups of atoms... (if) forces acting between them are such as to lead to the formation of an aggregate with sufficient stability to make it convenient for the chemist to consider it as an independent molecular species. Chemical bonds include ionic bonds, coordinate covalent... 

The term ceramics comes from the Greek keramikos, which means potter s clay or burnt stuff. While traditional ceramics were often based on natural clays, today s ceramics are largely synthetic materials. Depending on which ceramic and which definition is to be applied, ceramics have been described as inorganic ionic materials and as inorganic covalent (polymeric) materials. In fact, many ceramics contain both covalent and ionic bonds and can thus be considered to be or not to be (shades of Shakespeare) polymeric materials. Many of the new ceramics, such as the boron nitriles and the silicon carbides, are polymeric without containing any ionic bonds. 

It is once more apparent that not all compounds can be brought within the simple scheme of the ionic bond and it is difficult to say precisely where the division should be made. Carbon tetrachloride, for example, would be a volatile compound even if it were an ionic compound that in actual fact it is volatile does not necessarily prove that it is ionic, because it is known that there are other volatile compounds which are definitely not ionic. 

The term ionomer was originally introduced in 1964 by Dupont to indicate a thermoplastic polymer containing both covalent and ionic bonds (5-7). By definition, ionomers are statistical thermoplastic copolymers consisting of (8) ... 

The Ionic Bond and Other Electrostatic Bonds.—In case that there can be assigned to each of two atoms or groups of atoms a definite electronic structure essentially independent of the presence of the other atom or group and such that electrostatic interactions are set up that lead to strong at ruction and.the formation of a chemical bond, we say that the bond is an electrostatic bond. 

No oxygen is present in this reaction, so the traditional definition of oxidation will not help. But, since sodium is a metal, and metals lose electrons to nonmetals during the formation of an ionic bond, the sodium is oxidized in this reaction. 

The diatomic halides and oxides of the alkali and alkaline earth groups must, by definition, have a considerable ionic contribution to their bonding. These diatomics, together with those of Al, Ga and In, are in fact found to lie outside the predicted field for covalent bonds, as shown in Figure 5.6(d). Molecules with dative bonds are expected along the borderline between covalent and ionic types, including several fluorides (of Sb, Si, Sn, Pb, Be and Ag) and chlorides (Si, Sn). They are arbitrarily grouped with the more ionic bonds. 

Compounds, such as the polyhalides and polysulphides, formally also the azides, could be regarded as produced by the attachment of one or more neutral non-polar halogen, sulphur or nitrogen molecules to a halogen, sulphide or nitride ion. With the last one this way of representation is definitely incorrect the azide-ion N3 is linear in contrast to the triangular structure to be expected for ionic bonding. 

The difference between ceramics and cements, however, goes beyond this definition. From a structural viewpoint, the distinction between ceramics and cements concerns the interparticle bonds that holds them together and provides the necessary strength. Hydraulic cements are bonded by van der Waals forces, while ceramics are formed by either ionic or covalent bonds between their particles. Because covalent and ionic bonds are stronger than van der Waals bonds, ceramics have better strength than cements. 

Bohr theory (4.2) The first theory of the atom to propose that electrons in atoms were in definite energy levels, boiling point (14.2) The temperature at which a liquid changes to a gas at the prevailing pressure, boiling-point elevation (15.6) An increase in the boiling point of a solvent due to the presence of a solute, bond See covalent bond and ionic bond. bond order See total bond order. 

Since the analyte is often present in quite a complex matrix comprising other elements or substances that may or may not interfere with any projected method of determination, and may indeed be quite a minor constituent of the whole sample, these considerations will effectively dominate the working details of any analytical procedure. There can therefore be no case for prescribing a single definitive method for (say) nickel that would be universally applicable to its determination in alloys see Alloys), organometallic compounds see Organometallic Complexes), inorganic salts see Ionic Bonds), or coordination compounds see Coordination Complexes), to its presence as a trace constituent see Trace Element) in maize or other plant products, or in natural waters or effluents. 

In the first and second groups of the periodic table the 8 — N rule does not give the number of possible covalent bonds, furthermore the elements of these groups, together with those of the transition groups do not form homo-polar or ionic bonds but a metallic bond possessing definite characteristics. 

As the chemist has gained his sea legs in the use of wave mechanics he has attempted to define covalent and ionic character in terms of wave functions. The new point of view is presented, for example, by Coulson, who maintains, there are two distinct definitions of a covalent bond (447, p. 145). He proceeds to describe the bond wave function, first by a molecular orbital type approximation, and then by a valence bond type approximation. In either case the approximate wave functions consist of linear combinations of atomic orbitals. Partial ionic bonding is revealed by the magnitudes of coefficients which imply asymmetry of electron distribution. 

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