Covalent bonding within ions

Polyatomic Ions Covalent Bonds Within Ions Many ionic compounds contain polyatomic ions, which consist of two or more atoms bonded covalently and have a net positive or negative charge. For example, the ionic compound calcium carbonate is an array of polyatomic carbonate anions and monatomic calcium cations attracted to each other. The carbonate ion consists of a carbon atom covalently bonded to three oxygen atoms, and two additional electrons give the ion its 2- charge (Figure 2.15). In many reactions, a polyatomic ion stays together as a unit. 

Force Within Unit (Intra) covalent bond within polyatomic ion — — covalent bond... 

Force within units Covalent bond within polyatomic ion Atomic forces between subatomic particles Atomic forces between subatomic particles Covalent bond... 

A nonpolar liquid like heptane (C7H16) has intermolecular bonds with relatively weak London dispersion forces. Heptane is immiscible in water because the attraction that water molecules have for each other via hydrogen bonding is too strong. Unlike Na+ and CP ions, heptane molecules cannot break these bonds. Because bonds of similar strength must be broken and formed for solvation to occur, nonpolar substances tend to be soluble in nonpolar solvents, and ionic and polar substances are soluble in polar solvents like water. Polar molecules are often called hydrophilic and non-polar molecules are called hydrophobic. This observation is often stated as like dissolves like. Network solids (e.g., diamond) are soluble in neither polar nor nonpolar solvents because the covalent bonds within the solid are too strong for these solvents to break. 

Ans. (a) NiCE, (c) AEO3, and (d) NH4NO3 contain ionic bonds. NH4NO3 also has covalent bonds within each ion. (e) H2SO4 and (f) HCl wonld form ions if allowed to react with water. 

As with organic compounds, inorganic compounds can produce an infrared spectrum. Generally, the infrared bands for inorganic materials are broader, fewer in number and appear at lower wavenumbers than those observed for organic materials. If an inorganic compound forms covalent bonds within an ion, it can produce a characteristic infrared spectrum. The bands in the spectrum of ionic or coordination compounds will depend on the structure and orientation of the ion... 

The covalent bonding within a polyatomic ion such as NH4+ or S04 is very strong, but the forces that hold the entire substance together are ionic.Thus a compound that contains a polyatomic ion is an ionic compound (see Section 7-12). 

In an equation for dissociation, the charges must balance. For example, magnesium nitrate dissociates to give one magnesium ion for every two nitrate ions. However, only the ionic bonds between Mg + and NO3 are broken the covalent bonds within the polyatomic ion are retained. The dissociation for Mg(N03)2 is written as follows ... 

Phosphonate salte of tetravalent, trivalent, and divalent metal ions contain strong ionic-covalent bonds within the metal-oxygen sheets that determine the details of their lamellar structures. Tbe divalent metal (Zn2+ and Cu2+) compounds can be made nanoporous by various techniques, and subsequent intercalation by small molecules such as ammonia, amines, and other small molecules forms the basis for size- and shiqw-selective piezoelectric sensors. Several techniques have been developed for depositing these materials as thin Hlms on quartz crystal microbalance (QCM) devices. The most successful of these, in terms of eliminating interferences and speed of device response, involves layer-by-layer growth of films through adsorption of their components from non-aqueous solutions. 

In a nonpolymer molecule or molecular ion a limited number of atoms are linked by covalent bonds. The covalent forces within the molecule are considerably stronger than... 

The elements that are commonly part of organic compounds are all located in the upper right corner of the periodic table. They are all nonmetals. The bonds between atoms of these elements are essentially covalent. (Some organic molecules may form ions nevertheless, the bonds tvithin each organic ion are covalent. For example, the salt sodium acetate consists of sodium ions, Na+, and acetate ions, C2H,02. Despite the charge, the bonds within the acetate ion are all covalent.)... 

As Fig. 2.4 illustrates, a cation can associate with a surface as an inner sphere, or outer-sphere complex depending on whether a chemical, i.e., a largely covalent bond, between the metal and the electron donating oxygen ions, is formed (as in an inner-sphere type solute complex) or if a cation of opposite charge approaches the surface groups within a critical distance as with solute ion pairs the cation and the base are separated by one (or more) water molecules. Furthermore, ions may be in the diffuse swarm of the double layer. 

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. 

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