Properties of Monatomic Ions

So far we have focused on the reactants—the atoms—in the process of electron loss and gain. Now we focus on the products—the ions. We examine electron configurations, magnetic properties, and ionic radius relative to atomic radius. 

Electron Configurations of Main-Group Ions In Chapter 2, you learned the symbols and charges of many monatomic ions. But why does an ion have a particular charge in its compounds Why is a sodium ion Na and not Na , and why 

When an alkali metal atom [Group 1A(1)] loses its single valence electron, it becomes isoelectronic with the previous noble gas. The Na ion, for example, is isoelectronic with neon (Ne)  

Altematively, in the more common tin(II) ion (Sn ), the atom loses the two 5p electrons only and attains the stability of filled 55 and 4c/ sublevels  

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Trends in Metallic Behavior Properties of Monatomic Ions... 

Trends in Metallic Behavior 265 Properties of Monatomic Ions 266 CHAPTER REVIEW GUIDE 271 PROBLEMS 272... 

The solvation of polyatomic ions or polar neutral molecules is even more difficult to describe. There are two sources of additional problems first of all, the symmetry of the system under investigation is drastically reduced and hence the number of different configurations increases tremendously. Furthermore, the strength of the electric field is much smaller than in the case of monatomic ions with spherical symmetry and therefore the dynamic behavior of the solvation shell is even more important for a priori calculations of macroscopic properties. 

When an atom loses or gains electrons, it forms a monatomic ion, an ion from a single atom. (All the ions described in this section are monatomic ions.) The chemical properties of an ion are not at all like those of the atom from which it came the electrical charge becomes the dominant property. A sodium atom, Na, and a sodium ion, Na+, are chemically very different. Sodium atoms could never exist in contact with water, for example, because they react vigorously with water, but sodium ions exist in water without a problem. 

It is generally believed that the polarizabilities of monatomic ions and molecules are independent of field direction. For undistorted quasi-spherical molecules (e.g. CH4, CC14, etc.) the same is usually assumed. When two such atoms are held together, as in a diatomic molecule, the new system is not isotropically polarizable. The model discussed by Silberstein (1917) makes this understandable. If a unit field acts along the line of centres A-B it will induce primary moments parallel to itself in both A and B, and likewise if it acts at 90° to A-B. Each primary moment will induce a secondary moment in its neighbour in the first case the secondary moments will add to the primary moments, but in the second they will subtract. Hence b along the line of centres exceeds that across it, and the polarizability of A-B is an anisotropic property. A similar situation is to be expected with the majority of polyatomic ions or molecules (see Table 21). 

Frank and Robinson (1940) suggested that the partial molar entropy of the water in aqueous electrolyte solutions is affected by the structure-making or -breaking properties of their ions. Frank and Evans (1945) suggested that rather the entropies of hydration of the ions shed light on these properties. Gurney (1953) showed that a linear relationship exists between the partial molar entropy of monatomic ions, and their viscosity coefficients (see Sect. 3.1.1). Nightingale (1959) reverted to the Frank and Evans emphasize of partial molar entropies of hydration of the... 

In this article, we present a brief outline of the methods used and introduce the structural properties which can be calculated directly from the experimental data. Several examples have been selected to demonstrate the power of these methods, with reference to studies of monatomic ions such as Ni + and Cl (Figs. 1-3). We also mention an extension to the NDIS method that applies to aqueous solutions of null water and enables one to determine the nearest neighbour coordination of strong cations for cations which do not possess isotopes suitable for the NDIS method. ... 

To turn now to crystals composed of4 unattached atoms or monatomic ions, which ar6 individually isotropic. Here it is only the second factor —the effect of arrangement—which can be responsible for anisotropy in the crystal. It is the orderliness of arrangement itself which, because it gives rise to different atomic distributions in different directions (Fig. 2 c), confers properties varying with crystal direction. The degree of anisotropy is usually far less in these crystals than in crystals containing molecules or polyatomic ions which are themselves anisotropic. 

THE ZEEMAN EFFECT AND THE MAGNETIC PROPERTIES OF ATOMS AND MONATOMIC IONS... 

Besides chemical and physical properties and how these properties can be used for identification purposes, this experiment helps students learn the formulas and names of monatomic and polyatomic ions and allows them to observe light emission and absorption, which may be part of lecture discussions occurring at the same time. Since Parts A and B are done as a group, it also promotes teamwork. This is intended as a 2-week lab — Parts A and B the first week and Part C the next. With 10 ions to identify, Part C teaches time management. 

Answer (b) O and 10 are both neutral isotopes of oxygen and have the same chemical properties. The other pairs are also isotopes of one another, but in each case, one is neutral and the other an ion. Monatomic ions are not similar chemically to neutral atoms of the same element. 

In 1965 Edgell and co-workers reported an infrared band, from solutions of alkali metal salts of Co CO) dissolved in tetrahydrofuran (THF), which was assigned to the cation vibrating in a solvent cage. Subsequently a detailed report about the nature of the vibration of these monatomic ions in several non-aqueous solvents was given. The bands are broad and of medium intensity. Thus their properties are... 

It is regrettable that, in the past, different symbols have been adopted in compilations, but it is expected that, in the future, symbols advocated by I UP AC will be employed universally and that SI will be used for the units. To secure a further unification in thermodynamic tables, the International Council of Scientific Unions (ICSU) and the Committee on Data for Science and Technology (CODATA) set up in 1968 a Task Group on Key Values for Thermodynamics. The first objective of the Task Group is to prepare a set of values of the basic thermodynamic properties of a number of chemical species, to be agreed internationally. The set is to include the elements in both standard and monatomic gaseous states, aqueous ions, and simple compounds. ... 

The thing that makes the periodic table so helpful in writing chemical formulas is that all the elements in Group 2A/2 that form monatomic ions do so by losing two electrons. This loss of two electrons gives the elements of Group 2A/2 their similar chemical properties. 

The tin(II) and lead(II) ions, Sn + and Pb +, behave like other monatomic ions. Tin and lead in compounds in which the elements appear to have 4+ charges have properties that differ from the properties of other compounds made up of ions. This notwithstanding, the compounds are named as if they were made up of true ions. 

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