Sodium chloride, bonds

A pure covalent bond (an H-H bond for example) exhibits 0 % ionic character while a polar covalent bond like hydrogen fluoride (H-F) exhibits 42 % ionic character. Bonds in sodium chloride (NaCl) are normally considered as ionic. These sodium chloride bonds exhibit 72 % ionic character. This emphasizes that the transition between covalent bonds over polar covalent bonds to ionic bonds is very fluent. No bonds actually exhibit 100 % ionic character since the bond electrons always will be located around the less electronegative atom at least for just a very little percentage of the time. 

Ionic bonding was proposed by the German physicist Walther Kossel in 1916 in or der to explain the ability of substances such as molten sodium chloride to conduct an electric current He was the son of Albrecht Kossel winner of the 1910 Nobel Prize in physiology or medi cine for early studies in nu cleic acids... 

Direct Chlorination of Ethylene. Direct chlorination of ethylene is generally conducted in Hquid EDC in a bubble column reactor. Ethylene and chlorine dissolve in the Hquid phase and combine in a homogeneous catalytic reaction to form EDC. Under typical process conditions, the reaction rate is controlled by mass transfer, with absorption of ethylene as the limiting factor (77). Ferric chloride is a highly selective and efficient catalyst for this reaction, and is widely used commercially (78). Ferric chloride and sodium chloride [7647-14-5] mixtures have also been utilized for the catalyst (79), as have tetrachloroferrate compounds, eg, ammonium tetrachloroferrate [24411-12-9] NH FeCl (80). The reaction most likely proceeds through an electrophilic addition mechanism, in which the catalyst first polarizes chlorine, as shown in equation 5. The polarized chlorine molecule then acts as an electrophilic reagent to attack the double bond of ethylene, thereby faciHtating chlorine addition (eq. 6) ... 

The ionic bond is the most obvious sort of electrostatic attraction between positive and negative charges. It is typified by cohesion in sodium chloride. Other alkali halides (such as lithium fluoride), oxides (magnesia, alumina) and components of cement (hydrated carbonates and oxides) are wholly or partly held together by ionic bonds. 

Fig. 4.3. The formation of an ionic bond - in this case between a sodium atom and a chlorine atom, making sodium chloride.

Chemists refer to the bond in a molecule like sodium chloride as ionic , meaning that its electron pair resides entirely on chlorine. At the other extreme is the covalent bond in the hydrogen molecule, where the electron pair is shared equally between the two hydrogens. Intermediate cases, such as the bond in hydrogen fluoride which is clearly polarized toward fluorine, are generally referred to as polar covalent bonds (rather than partially ionic bonds). Are these situations really all different or do they instead represent different degrees of the same thing ... 

Galvanised steel provides increased corrosion resistance in carbonated concrete. In concrete with more than 0.4% chloride ion with respect to the cement content, there is an increased risk of corrosion and at high chloride contents the rate of corrosion approaches that of plain carbon steel. In test conditions the rate of corrosion is greater in the presence of sodium chloride than calcium chloride. Fusion-bonded epoxy-coated steel performs well in chloride-contaminated concrete up to about 3.9% chloride ion in content. 

The charges of the ions. The bond in CaO (+2, —2 ions) is considerably stronger than that in NaCl (+1,-1 ions). This explains why the melting point of calcium oxide (2927°C) is so much higher than that of sodium chloride (801°C). 

The ionic model, the description of bonding in terms of ions, is particularly appropriate for describing binary compounds formed from a metallic element, especially an s-block metal, and a nonmetallic element. An ionic solid is an assembly of cations and anions stacked together in a regular array. In sodium chloride, sodium ions alternate with chloride ions, and large numbers of oppositely charged ions are lined up in all three dimensions (Fig. 2.1). Ionic solids are examples of crystalline... 

Sometimes the atomic arrangement of a crystal is such as not to permit the formulation of a covalent structure. This is the case for the sodium chloride arrangement, as the alkali halides do not contain enough electrons to form bonds between each atom and its six equivalent nearest neighbors. This criterion must be applied with caution, however, for in some cases electron pairs may jump around in the crystal, giving more bonds than there are electron pairs, each bond being of an intermediate type. It must also be mentioned that determinations of the atomic arrangement are sometimes not sufficiently accurate to provide evidence on this point an atom reported equidistant from six others may be somewhat closer to three, say, than to the other three. 

In the classroom, ionic bonding is mostly introduced by the example of simple ionic substances like sodium chloride. Starting from the electronic configuration of... 

Organic chemistry and covalent bonding Liebig (1803-1873) the particles of sodium chloride as pairs and not as single ions. Schmidt (1992) The importance of isomerism... 

In crystalline sodium chloride, sodium and chlorine atoms are arranged at the corners of cubes in such a manner that each chlorine atom is immediately adjacent to only sodium atoms and each sodium atom is immediately adjacent to only chlorine atoms. This arrangement gives a high degree of stability because of the large number of bonds between unlike or oppositely charged atoms. The common habit is the cube. 

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