Cations polyatomic

Polyatomic Cations. Polyatomic cations derived by addition of more protons than required to give a neutral unit to polyatomic anions are named by adding the ending -onium to the root of the name of the anion element for example, PH4, phosphonium ion HjU, iodonium ion H3O+, oxonium ion CH3OHJ, methyl oxonium ion. 

Diffraction studies on the structures of doped polyparaphenylene show that although the polymer chains retain their nonzero setting angles in the presence of alkali metal cations, polyatomic ions such as AsF6 may well impose an all-parallel arrangement on polymers [see Fig. 5.8(d) and Stamm and Hocker s comments on the most favored structure of AsFs-doped polyparaphenylene]. The latter structure is rather similar to that foimd in the simulated doped PPy and PTh lattices, with the ions occupying sites that are coplanar with the chains. 

This principle also applies to polyatomic cations corresponding to radicals with special names ending in -yl (Sec. 3.1.2.10) for example, PO+, phosphoryl cation NO+, nitrosyl cation NOj, nitryl cation O2+, oxygenyl cation. 

The probable crystal stmcture of this salt has been described (14) as a complex of two dianions and two cations forming a large polyatomic ring. By implication this type of molecular packing probably appHes to many other similar pigments. 

Pu(IV) forms polyatomic complexes with inorganic and organic ligands. As the number of anionic ligands increases, cationic, neutral, and anionic complexes form and the sequential stabiUty constants, typically decrease. For the following reaction, where M is Pu + and L is a ligand,... 

In addition to the Zachariasen and radius ratio rules, for oxides the electronegativity of the predominant cation should be between 1.7 and 2.1 (7). If the cation electronegativity is too high, the compound tends to form molecules or discrete polyatomic ions rather than a connected network. For example, CrO satisfies the radius ratio rule, but the highly electronegative Cr ions promote the formation of discrete dichromate(VI) ions, Cr202 , in the presence of other oxides. 

Other less-symmetrical coordination geometries for Se and Te occur in the /t,-Se2 and /t-Te2 complexes and the polyatomic cluster cations Seio and Tee" " ", as mentioned below. 

Nearly all cations are monatomic the majority of anions are polyatomic. 

Similar relationships hold for ionic solids containing polyatomic ions (Table 2.2) or transition metal cations (Figure 4.2). 

Count the number of valence electrons. For a molecule, simply sum up the valence electrons of the atoms present. For a polyatomic anion, one electron is added for each unit of negative charge. For a polyatomic cation, a number of electrons equal to the positive charge must be subtracted. 

Hg22+ is a polyatomic cation there is a covalent bond between the mercury atoms. 

Polysulfides have been prepared with many different types of cations, both monoatomic Hke alkah metal ions and polyatomic Hke ammonium or substituted ammonium or phosphonium ions. In this chapter only those salts will be discussed in detail which contain univalent main-group cations although a large number of transition metal polysulfido complexes have been prepared [7-9]. 

Two important polyatomic cations appear in introductory chemistry. These are the ammonium ion, NHJ, and the hydronium ion, H3 O, both of which are shown in Figure 3-11. These cations always have H-1 charges. The... 

NH4HSO4 The polyatomic ammonium cation is combined with a hydrogen-containing anion ammonium hydrogen sulfate. 

When a salt containing polyatomic ions dissolves In water, the cations separate from the anions, but each polyatomic ion remains intact. An example Is ammonium nitrate, composed of NH4 polyatomic cations and NO3 polyatomic anions. Ammonium nitrate dissolves In water to give a solution containing NH4 cations and NO3 anions, as Figure 3-21 Illustrates. 

Although the nonmetals do not readily form cations, many of them combine with oxygen to form polyatomic oxoanions. These anions have various stoichiometries, but there are some common patterns. Two second-row elements form oxoanions with three oxygen atoms carbon (four valence electrons) forms carbonate, C03, and nitrogen (five valence electrons) forms nitrate, NO3. In the third row, the most stable oxoanions contain four oxygen atoms Si04 -, P04 -, S04, and CI04. ... 

Minerals often contain more than one cation or anion. For example, apatite, Caj ( 04)3 F, contains both phosphate and fluoride anions. Beryl, Bc3 AI2 Sig Oig, contains beryllium and aluminum cations as well as the Sig Oig polyatomic anion. An even more complicated example is gamierite, (Ni,Mg)e Si4 0io(OH)2,... 

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