Group IIA ions

La3+155 q 3+156 fQj. Ni-Mo/Al203 Group IA and IIA ions, Group IIA ions/ The structural effect of dopant ions (Na, Mg, and Zn + 97 y jg partly to neutralize acid sites on the catalyst surface and partly to displace or from the AI2O3 lattice to the surface, so... 

Group IIA ion transport,. 569 Stabilization image dyes photography. 112 silver halides... 

Hydrogen sulfide gas is used in analytical chemistry laboratories to detect certain metal ions in a solution. If the solution contains a Group IIA metal, such as calcium, a precipitate will form when an acidic solution containing hydrogen sulfide is added to it. The precipitate forms because one of the products of the chemical reaction is insoluble (which means it does not dissolve). 

The elements that form only one cation are the alkali metals (group IA), the alkaline earth metals (group IIA), zinc, cadmium, aluminum, and most often silver. The charge on the ions that these elements form in their compounds is always equal to their periodic table group number (or group number minus 10 in the newest labeling system in the periodic table). 

Am. In each ease, the answer is BuS. Part (ft) gives the ions and their charges, and so is perhaps easiest to answer. Part (know that periodic group IIA elements always form 2-t- ions in all their compounds and that sulfur forms a 2- ion in its compounds with metals. It is also necessary to remember that the metal is named first. In part (< ). the fact that there is only one compound of these two elements is deduced by the fact that the barium is stated with no Roman numeral, and that sulfide is a specific ion with a specific (2-) charge. 

This Group IIA (or Group 2) element (atomic symbol, Ca atomic number, 20 atomic weight, 40.078 electronic configuration = ls 2s 2p 3s 3p 4s ) loses both As electrons to form a divalent cation of 0.99A ionic radius. Ionic calcium combines readily with oxygen ligands (chiefly water, phosphates, polyphosphates, and carbox-ylates) to form stable metal ion complexes. Ca under-... 

A< Ba(Q02)2.Bcirium is an alkaline ecirth metal (Group IIA) and thus has a chcii e of -1-2. You should recognize chlorite as the name of a polyatomic ion. In fact, any anion name that doesn t end in -ide should scream polyatomic ion to you. As Table 6-1 shows, chlorite is ClOj , which reveals that the chlorite ion has a-1 charge. Two chlorite ions cire necessary to neutralize the -1-2 chcirge of a single barium cation, so the chemical formula is Ba(C102)2-... 

Table 4 lists some antibiotics that function as ionophores, including some that bind Group IIA cations. Ionophores may be classed as channel formers or carriers by several approaches. A carrier ionophore is dependent on membrane fluidity and so cannot function below the transition temperature of the phospholipids in the membrane, as these are now frozen . The channel formers are much less dependent on membrane fluidity. A channel-forming ionophore cannot function if it fails to span the membrane, and so if an ionophore ceases to function in thicker membranes then it is probably a channel former. The kinetics of ion transport may provide a good indication of the type of ionophore. If an ionophore functions at a rate of more than 104 ions s 1 then it must be a channel former, as this level of ion flux cannot be provided by the diffusion of a carrier complex across the membrane. 

As will be discussed in greater detail later, some of the naturally occurring minerals of the Group IIA metals are of great importance. Some of the properties of atoms and ions of the Group IIA elements are shown in Table 7.6. 

Table 7.6 Characteristics of Atoms and Ions of Group IIA Elements...

It should be recognized that the Na2Be02 and Na2Be(OH)4 are equivalent if the latter has two molecules of water removed. Also as a result of the small size of the Be2+ ion, beryllium is four coordinate in most of its compounds, but the other members of Group IIA are most often six coordinate. 

All of the Group IA and IIA metals form sulfides, some of which are used rather extensively. The sulfides of Group IIA metals consist of M2+ and S2 ions arranged in the sodium chloride type lattice (see Chapter 3). The compounds of the Group IA metals consist of M+ and S2, but as a result of there being twice as many cations as anions, the structure is of the antifluorite type (see Chapter 3). The sulfide ion is a base so there is extensive hydrolysis in solutions of the sulfides, and the solutions are basic ... 

The ability of crown ethers to bind selectively to particular Group IA and Group IIA metal ions, because of the relationship between hole size and metal ion radius, has led to considerable interest in them in relation to membranes (models for selective ion transport), antibiotics (similar polyether structure), organic synthesis [solubilization of inorganic reagents leading to milder routes for oxidation (122), nucleophilic substitution (123), fluoridation (90)] and extraction of alkali... 

Which metals in each of the following periodic groups form ions of only one charge (a) lA, (b) IIA,... 

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