The Formation and Nature of Ionic Bonds

To bond ionically, atoms must transfer valence electrons. An atom that loses one or more electrons becomes a positive ion. An atom that gains one or more electrons becomes a negative ion. The ionic bond that forms is the electrostatic force holding the oppositely charged ions together. 

The total number of electrons lost must equal the total number of electrons gained. The ratio of atoms that bond ionically must therefore be such that overall electrical neutrality is maintained. 

A neutral atom of magnesium has the electron configuration ls 2s 2p 3s, or, in abbreviated form, [Ne]3s. Chlorine has the electron configuration [Ne]3s 3p. An atom of Mg would lose its two valence electrons to form a 2+ ion and achieve the stable electron configuration of a noble gas. An atom of Cl would gain one electron to form a 1 - ion. To achieve overall neutrality in the compound, each Mg ion would require two Cl ions (1 x 2+) + 

Write the electron configurations, in abbreviated form, for the atoms in each pair, referring to the periodic table as necessary. Then determine the ratio of the atoms in the ionic compound formed in each case. 

For each of the following pairs of ionic compounds, state which would he expected to have the higher (more negative) lattice energy. 

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  

Consider the formation of the ionic compound calcium fluoride from calcium (Ca) and fluorine (F). Calcium, a group 2A metal with the electron configuration [Ar]4s, has two valence electrons. Fluorine, a group 7A nonmetal with the electron configuration [He]2s 2p, must gain one electron to attain the noble gas configuration of neon. 

These chemical reactions that produce ionic compounds also release a large amount of energy. 

Q The reaction that occurs between elemental sodium and chlorine gas produces a white crystalline solid, o This sparkler contains iron, which burns in air to produce an ionic compound that contains iron and oxygen. 

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The chemisorptive bond is a chemical bond. The nature of this bond can be covalent or can have a strong ionic character. The formation of the chemisorptive bond in general involves either donation of electrons from the adsorbate to the metal (donation) or donation of electrons from the metal to the adsorbate (backdonation).2 In the former case the adsorbate is termed electron donor, in the latter case it is termed electron acceptor.3 In many cases both donation and backdonation of electrons is involved in chemisorptive bond formation and the adsorbate behaves both as an electron acceptor and as an electron donor. A typical example is the chemisorption of CO on transition metals where, according to the model first described by Blyholder,4 the chemisorptive bond formation involves both donation of electrons from the 7t orbitals of CO to the metal and backdonation of electrons from the metal to the antibonding n orbitals of CO. 

As already mentioned, the criterion of complete ionization is the fulfilment of the Kohlrausch and Onsager equations (2.4.15) and (2.4.26) stating that the molar conductivity of the solution has to decrease linearly with the square root of its concentration. However, these relationships are valid at moderate concentrations only. At high concentrations, distinct deviations are observed which can partly be ascribed to non-bonding electrostatic and other interaction of more complicated nature (cf. p. 38) and partly to ionic bond formation between ions of opposite charge, i.e. to ion association (ion-pair formation). The separation of these two effects is indeed rather difficult. 

Only a limited number of monomer pairs form block copolymers in this manner. Examples are conjugated dienes and vinyl aromatics that have similar Q-e values. The nature of the anionic initiator, i.e., the ionic character of the carbon-metal bond plays an important role in both the amount and sequence of block formation. For instance, when potassium or cesium initiators are used, styrene polymerizes first as can be seen in Figure 12. 

Owing to the presence of many amine, carboxylic acid, amide, and other polar groups, wool and silk are hydrophilic in nature, wetted by water, and are dyed with either acid or basic dyes through the formation of ionic bonds (salt linkages). They may also be dyed with reactive dyes that form covalent bonds with available amino groups. 

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