Ionic solid forces

Ion-exchange methods are based essentially on a reversible exchange of ions between an external liquid phase and an ionic solid phase. The solid phase consists of a polymeric matrix, insoluble, but permeable, which contains fixed charge groups and mobile counter ions of opposite charge. These counter ions can be exchanged for other ions in the external liquid phase. Enrichment of one or several of the components is obtained if selective exchange forces are operative. The method is limited to substances at least partially in ionized form. 

The force of attraction between H20 molecules and the ions, which tends to bring the solid into solution. If this factor predominates, the compound is very soluble in water, as is the case with NaCl, NaOH, and many other ionic solids. 

The force of attraction between oppositely charged ions, which tends to keep them in the solid state. If this is the major factor, the water solubility is very low. The fact that CaC03 and BaS04 are almost insoluble in water implies that interionic attractive forces predominate with these ionic solids. 

The molecules (or atoms, for noble gases) of a molecular solid are held In place by the types of forces already discussed In this chapter dispersion forces, dipolar interactions, and/or hydrogen bonds. The atoms of a metallic solid are held in place by the delocalized bonding described in Section 10-. A network solid contains an array of covalent bonds linking every atom to its neighbors. An ionic solid contains cations and anions, attracted to one another by electrical forces as described in Section 8-. 

As described in Chapter 8, ionic solids contain cations and anions strongly attracted to each other by electrical forces. These forces act between ions rather than between molecules. Ionic solids must be electrically neutral, so their stoichiometries are determined by the charges carried by the positive and negative ions. 

Water is highly polar, but it is not ionic. How, then, can water act as a solvent for ionic solids A salt dissolves only if the interactions between the ions and the solvent are strong enough to overcome the attractive forces that hold ions in the ciystal lattice. When an ionic solid forms an aqueous solution, the cations and anions are solvated by strong ion-dipole interactions with water molecules. 

These forces affect the boiling point, melting point, hardness, and electrical and heat conductivity of a substance. In this chapter, we will study metals, ionic solids, network solids, dipole-dipole attractions, van der Waals forces and hydrogen bonds. 

Ionic solids have their lattices composed of ions held together by the attraction of opposite charges of the ions. These crystalline solids tend to be strong with high melting points due to the strength of the intermolecular forces. NaCl and other salts are example of ionic solids. 

Sodium chloride and other soluble ionic solids dissolve in polar solvents such as water because of ion-dipole forces. An ion-dipole force is the force of attraction between an ion and a polar molecule (a dipole). For example, NaCl dissolves in water because the attractions between the Na and Cl ions and the water molecules provide enough energy to overcome the forces that bind the ions together. Figure 4.14 shows how ion-dipole forces dissolve any type of soluble ionic compound. 

Identify forces of attraction and repulsion that occur in molecules and in ionic solids. 

The melting point of NaCl is 801°C, of CaCl2 is 782°C, and of AICI3 is 190°C. The electrostatic forces of attraction between ions increase with an increase in the charge. In these ionic solids, the charge on the cations Na", Ca ", and Al ... 

Ionic solids are also called salts. Salts are composed of atoms held together by ionic bonds. These bonds are the result of electrostatic attractions between positively charged ions (cations ) and negatively charged ions (anions). The force of electrostatic attraction is inversely related to the square of the distance of separation of the ions (Eq. 2.1). 

Condensed matter can be classified by the nature of the forces that hold it together ionic solids covalent solids metallic solids molecular solids. 

The oxidizers used in high-energy mixtures are generally ionic solids, and the "looseness" of the ionic lattice is quite important in determining their reactivity [3]. A crystalline lattice has some vibrational motion at normal room temperature, and the amplitude of this vibration increases as the temperature of the solid is raised. At the melting point, the forces holding the crystalline solid to-... 

Ionic Bond intramolecular force created when electrons are transferred from one atom to another creating ions that possess electrostatic attraction for one another Ionic Solid a solid composed of anions and cations such as NaCl... 

A gradient of electrical potential constitutes the classic (external) force field for ionic solids. Let us study the effect of this electric field on the interface morphology and stability. The thermodynamic driving force in ionic crystals is Vi/,(= +... 

FIGURE 2.4 This sequence of images illustrates why ionic solids are brittle, (a) The original solid consists of an orderly array of cations and anions, (b) A hammer blow can push the ions into positions where cations are next to cations and anions are next to anions there are now strong repulsive forces acting (as depicted by the doubleheaded arrows), (c) As a result of these repulsive forces, the solid breaks apart into fragments. 

The oppositely charged Na+ and Cl- ions that result when sodium transfers an electron to chlorine are attracted to one another by electrostatic forces, and we say that they are joined by an ionic bond. The crystalline substance that results is said to be an ionic solid. A visible crystal of sodium chloride does not consist of individual pairs of Na+ and Cl- ions, however. Instead, solid NaCl consists of a vast three-dimensional network of ions in which each Na+ is surrounded by and attracted to many Cl - ions, and each Cl- is surrounded by and attracted to many Na+ ions (Figure 6.7). 

---