Anion polyatomic anions

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. 

See Secs. 3.1.2.2 and 3.1.2.8 for naming monatomic and certain polyatomic anions. When an organic group occurs in an inorganic compound, organic nomenclature (q.v.) is followed to name the organic part. 

Protonated Anions. Ions such as HSOy are recommended to be named hydrogensulfate with the two words written as one following the usual practice for polyatomic anions. However, in the Nomenclature of Organic Chemistry, 1979 edition, hydrogen is used as a separate word this practice is followed in this Handbook. 

Other Polyatomic Anions. Names for other polyatomic anions consist of the root name of the central atom with the ending -ate and followed by the valence of the central atom expressed by its oxidation number. Atoms and groups attached to the central atom are treated as ligands in a complex. 

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. 

For other polyatomic anions, find the name of the ion in Table D.l or Appendix 3A. If hydrogen is present, add hydrogen" to the name of the anion. If two hydrogen atoms are present, add dihydrogen to the name of the anion. 

Carbon is the only Group 14/IV element that forms both monatomic and polyatomic anions. There are three classes of carbides saline carbides (saltlike carbides), covalent carbides, and interstitial carbides. The heavier elements in Group 14/IV form polyatomic anions, such as Si44 and Sn52, in which the atoms form a tetrahedron and trigonal bipyramid, respectively. 

The azide ion is a highly reactive polyatomic anion of nitrogen, N3 . Its most common salt, sodium azide, NaN3, is prepared from dinitrogen oxide and molten sodium amide ... 

There are many different polyatomic anions, including several that are abundant in nature. Each is a stable chemical species that maintains its stmcture in the solid state and in aqueous solution. Polyatomic anions are treated as distinct units when writing chemical formulas, naming compounds, or drawing molecular pictures. The names, formulas, and charges of the more common polyatomic anions are listed in Table 3-4. You should memorize the common polyatomic ions because they appear regularly throughout this textbook. 

Most polyatomic anions contain a central atom surrounded by one to four oxygen atoms. These species are called oxoanions, and they are named according to the following guidelines ... 

CaCl2 Ammonium is not present, but there is a metal (Ca). There is no polyatomic anion, but Ca is from Group 2, and there is a halide (Cl), so this compound is ionic. 

Magnesium nitrate contains (Group 2) and the polyatomic anion NO3 . Again, there must be... 

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. 

Closely related to silica are the silicate minerals, all of which contain polyatomic anions made of silicon and oxygen. The simplest silicates, called orthosilicates, contain Si04 anions. The 8104 anion is tetrahedral, with a central silicon atom bonded to four outer oxygen atoms. 

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,... 

The name of each oxoacid is based on the name of the polyatomic anion from which it forms, followed by the word acid. Review Table for the names of common polyatomic anions. 

An oxoacid that forms from a polyatomic anion whose name ends in -ate has a name ending in -ic. For example, HNO3 forms by adding a proton to the nitrate polyatomic anion, so HNO3 is nitric acid. Likewise, HCIO4 is perchloric acid from the perchlorate anion. 

FeC03 This ionic compound contains the carbonate polyatomic anion, C O3. The -2 charge on carbonate requires that iron have +2 oxidation number (Guideline 2). In the carbonate anion, each oxygen atom is -2, for a total of-6. The oxidation numbers must add up to the net charge on the anion (-2), so the carbon atom must have an oxidation number of +4. 

A soft Lewis base has a large donor atom of high polarizability and low electronegativity. Iodide ion has its valence electrons in large a = 5 orbitals, making this anion highly polarizable and a very soft base. Other molecules and polyatomic anions with donor atoms from rows 3 to 6 are also soft bases. To summarize, the donor atom becomes softer from top to bottom of a column of the periodic table. 

Some nonmetals form complex (polyatomic) anions, which consist of a group of three or more atoms bearing a negative charge. 

Sulfide ions in solution react with sulfur to produce polyatomic anions known as the polysulfides. When... 

A cation containing two xenon atoms, Xe2Fu+, is also known, and it has a structure that can be shown as F5Xe+"-F -" XeF5+. Polyatomic anions containing xenon are produced because XeFs is also a Lewis acid. An example of this type of reaction can be shown as... 

The group of the chalcogens sulfur, selenium and tellurium is a typical triad of the more electronegative nonmetals with relatively high-ionization energies, relatively strong element-element bonds and a clear tendency to form mono-and polyatomic anions (Table 1). 

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