Ionic compound cation

Ionic compounds Cations and anions NaCl Ionic bond... 

A complex ion consists of a central metal ion bonded to molecules or anions called ligands. Complex ions form in a stepwise process characterized by a formation constant, Kf, that is much greater than 1. Adding an anion that can act as a ligand increases the solubility of a slightly soluble ionic compound because it forms a complex ion with the ionic compounds cation. (Section 19.4)... 

The co-ordination number in ionic compounds is determined by the radius ratio - a measure of the necessity to minimize cationic contacts. More subtle effects are the Jahn-Teller effect (distortions due to incomplete occupancy of degenerate orbitals) and metal-metal bonding. 

To date there is no evidence that sodium forms any chloride other than NaCl indeed the electronic theory of valency predicts that Na" and CU, with their noble gas configurations, are likely to be the most stable ionic species. However, since some noble gas atoms can lose electrons to form cations (p. 354) we cannot rely fully on this theory. We therefore need to examine the evidence provided by energetic data. Let us consider the formation of a number of possible ionic compounds and first, the formation of sodium dichloride , NaCl2. The energy diagram for the formation of this hypothetical compound follows the pattern of that for NaCl but an additional endothermic step is added for the second ionisation energy of sodium. The lattice energy is calculated on the assumption that the compound is ionic and that Na is comparable in size with Mg ". The data are summarised below (standard enthalpies in kJ) ... 

Many elements readily form ionic compounds such as table salt (Na Cl ), iu which the cationic sodium and anionic chlorine are held... 

Whether an element is the source of the cation or anion in an ionic bond depends on several factors for which the periodic table can serve as a guide In forming ionic compounds elements at the left of the periodic table typically lose electrons giving a cation that has the same electron configuration as the nearest noble gas Loss of an elec tron from sodium for example yields Na which has the same electron configuration as neon... 

Electrically assisted transdermal dmg deflvery, ie, electrotransport or iontophoresis, involves the three key transport processes of passive diffusion, electromigration, and electro osmosis. In passive diffusion, which plays a relatively small role in the transport of ionic compounds, the permeation rate of a compound is deterrnined by its diffusion coefficient and the concentration gradient. Electromigration is the transport of electrically charged ions in an electrical field, that is, the movement of anions and cations toward the anode and cathode, respectively. Electro osmosis is the volume flow of solvent through an electrically charged membrane or tissue in the presence of an appHed electrical field. As the solvent moves, it carries dissolved solutes. 

In the absence of die polyether, potassium fluoride is insoluble in benzene and unreactive toward alkyl halides. Similar enhancement of solubility and reactivity of other salts is observed in the presence of crown ethers The solubility and reactivity enhancement result because the ionic compound is dissociated to a tightly complexed cation and a naked anion. Figure 4.13 shows the tight coordination that can be achieved with a typical crown ether. The complexed cation, because it is surrounded by the nonpolar crown ether, has high solubility in the nonpolar media. To maintain electroneutrality, the anion is also transported into the solvent. The cation is shielded from interaction with the anion as a... 

Because a bulk sample of matter is electrically neutral, ionic compounds always contain both cations (positively charged particles) and anions (negatively charged particles). Ordinary table salt, sodium chloride, is made up of an equal number of Na+ and Cl- ions. The structure of sodium chloride is shown in Figure 2.11. Notice that—... 

Strategy Once you deduce the formula of the ionic compound, it s all downhill. Remember, though, that you have to show the relative numbers of cations and anions. 

When a metal such as sodium (Na) or calcium (Ca) reacts with a nonmetal such as chlorine (Cl2), the product is ordinarily an ionic compound. The formula of that compound (e.g., NaCl, CaCl2) shows the simplest ratio between cation and anion (one Na+ ion for one Cl ion one Ca2+ ion for two Cl- ions). In that sense, the formulas of ionic compounds are simplest formulas. Notice that the symbol of the metal (Na, Ca) always appears first in the formula, followed by that of the nonmetal. 

To predict the formula of an ionic compound, you need to know the charges of the two ions involved. Then you can apply the principle of electrical neutrality, which requires that the total positive charge of the cations in the formula must equal the total negative charge of the anions. Consider, for example, the ionic compound calcium chloride. The ions present are Ca2+ and Cl-. For the compound to be electrically neutral, there must be two Cl- ions for every Ca2+ ion. The formula of calcium chloride must be CaCl indicating that the simplest ratio of Cl- to Ca2+ ions is 2 1. 

The name of an ionic compound consists of two words. The first word names the cation and the second names the anion. This is, of course, the same order in which the ions appear in the formula. 

Sometimes when water solutions of two different ionic compounds are mixed, an insoluble solid separates out of solution. The precipitate that forms is itself ionic the cation comes from one solution, the anion from the other. To predict the occurrence of reactions of this type, you must know which ionic substances are insoluble in water. 

As a result of these effects, anions in general are larger than cations. Compare, for example, the Cl- ion (radius = 0.181 nm) with the Na+ ion (radius = 0.095 nm). This means that in sodium chloride, and indeed in the vast majority of all ionic compounds, most of the space in the crystal lattice is taken up by anions. 

In previous chapters we have referred from time to time to compounds of the transition metals. Many of these have relatively simple formulas such as CuSO CrCI3, and FetNO These compounds are ionic The transition metal is present as a simple cation (Cu2+, Cr3+, Fe3+). In that sense, they resemble the ionic compounds formed by the main-group metals, such as CaS04 and AKNOJ ... 

Coordination compounds are named in much the same way as simple ionic compounds. The cation is named first, followed by the anion. Examples include... 

Solomon, Kinetics of Synthesis and Decomposition Reactions of Ionic Compounds Containing N-F Cations , Illinois Institute of Technology Research Institute, IITRI C-6140 (Jan 1969), AD-682497, p 5 CA 77, 131206 (1972)... 

The formulas of ionic compounds have a different meaning from those of molecular compounds. Each crystal of sodium chloride has a different total number of cations and anions. We cannot simply specify the numbers of ions present as the formula of this ionic compound, because each crystal would have a different formula and the subscripts would be enormous numbers. However, the ratio of the number of cations to the number of anions is the same in all the crystals, and the chemical formula shows this ratio. In sodium chloride, there is one Na+ ion for each Cl ion so its formula is NaCl. Sodium chloride is an example of a binary ionic compound, a compound formed from the ions of two elements. Another binary compound, CaCl2, is formed from Ca2+ and Cl- ions in the ratio 1 2, which is required for electrical neutrality. 

D.1 Names of Cations D.2 Names of Anions D.3 Names of Ionic Compounds D.4 Names of Inorganic Molecular Compounds D.5 Names of Some Common Organic Compounds... 

An ionic compound is named with the cation name first, followed by the name of the anion the word ion is omitted in each case. The oxidation number of the cation is given if more than one charge is possible. However, if the cation comes from an element that exists in only one charge state (as listed in Fig. C.6), then the oxidation number is omitted. Typical names include potassium chloride (KC1), a compound containing K+ and Cl" ions and ammonium nitrate (NH4NOs), which contains NH4+ and NO3" ions. The cobalt chloride that contains Co2+ ions (CoCl,) is called cobalt(II) chloride C0CI3 contains Co3+ ions and is called cobalt(III) chloride. 

Ionic compounds are named by starting with the name of the cation (with its oxidation number if more than one charge is possible), followed by the name of the anion hydrates are named by adding the word hydrate, preceded by a Greek prefix indicating the number of water molecules in the formula unit. 

Some ionic compounds are soluble, others are not. Consider what happens when we pour a solution of sodium chloride (a strong electrolyte) into a solution of silver nitrate (another strong electrolyte). A solution of sodium chloride contains Na+ cations and Cl anions. Similarly, a solution of silver nitrate, AgNO, contains Ag+ cations and NO, anions. When we mix these two aqueous solutions, a white precipitate, a cloudy, finely divided solid deposit, forms immediately. Analysis shows that the precipitate is silver chloride, AgCl, an insoluble white solid. The... 

To understand why a crystal of sodium chloride, an ionic compound, has a lower energy than widely separated sodium and chlorine atoms, we picture the formation of the solid as taking place in three steps sodium atoms release electrons, these electrons attach to chlorine atoms, and then the resulting cations and anions clump together as a crystal. Chemists often analyze complex processes by breaking them down into simpler steps such as these, and often consider hypothetical steps (steps that do not actually occur). 

When the radius ratio of an ionic compound is less than about 0.4, corresponding to cations that are significantly smaller than the anion, the small tetrahedral holes may be occupied. An example is the zinc-blende structure (which is also called the sphalerite structure), named after a form of the mineral ZnS (Fig. 5.43). This structure is based on an expanded cubic close-packed lattice of the big S2 anions, with the small Zn2+ cations occupying half the tetrahedral holes. Each Zn2+ ion is surrounded by four S2 ions, and each S2" ion is surrounded by four Zn2+ ions so the zinc-blende structure has (4,4)-coordination. 

FIGURE 5.46 (a) When a metal s cations are displaced by a blow from a hammer, the mobile electrons can immediately respond and follow the cations to their new positions, and consequently the metal is malleable, (b) This piece of lead nas been flattened by a hammer, whereas crystals of the orange-colored ionic compound leaddl) oxide have shattered. 

Many ionic compounds are considered to pack in such as way that the anions form a close-packed lattice in which the metal cations fill holes or interstitial sites left between the anions. These lattices, however, may not necessarily he as tightly packed as the label close-packed implies. The radius of an F ion is approximately 133 pm. The edge distances of the cubic unit cells of LiF, NaF, KF, RbF, and CsF, all of which... 

The principal product of the reaction of the alkali metals with oxygen varies systematically down the group (Fig. 14.15). Ionic compounds formed from cations and anions of similar radius are commonly found to he more stable than those formed from ions with markedly different radii. Such is the case here. Lithium forms mainly the oxide, Li20. Sodium, which has a larger cation, forms predominantly the very pale yellow sodium peroxide, Na202. Potassium, with an even bigger cation, forms mainly the superoxide, K02, which contains the superoxide ion, O,. ... 

Diborane reacts with ammonia to form an ionic compound (there are no other products). The cation and anion each contain one boron atom, (a) Predict the identity and formula of each ion. (b) Give the hybridization of each boron atom, (c) Identify the type of reaction that has occurred (redox, Lewis acid-base, or Bronsted acid-base). 

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