Negative polyatomic ion

As discussed above, a number of doubly-charged negative polyatomic ions have been reported by several observers. As the molecule becomes quite large, the problems due to Coulombic repulsion are reduced by increased separation of charge. Thus, the more important species to examine here are the smaller polyatomic molecules. In particular, the reported SFs and SFg are deemed interesting by virtue of the fact that both SFs and SFe are well known species in the gas phase. 

What does it mean to be a hydrogen-ion donor or a hydrogen-ion acceptor The symbols X and Y may be used to represent nonmetallic elements or negative polyatomic ions. Thus the general formula for an acid can be written as HX or HY. When a molecule of acid, HX, dissolves in water, it donates a H+ ion to a water molecule. The water molecule acts as a base and accepts the H+ ion. 

Using the negative polyatomic ions listed in Table 5.4, write formulas for each of their sodium and calcium compounds. 

A polyatomic ion is an ion that contains two or more elements. Compounds containing polyatomic ions are composed of three or more elements and usually consist of one or more cations combined with a negative polyatomic ion. In general, naming compounds containing polyatomic ions is similar to naming binary compounds. The cation is named first, followed by the name for the negative polyatomic ion. 

For an ionic compound, you must next decide whether the metal forms only one type of ion or more than one type of ion. Group lA (alkali) mefals. Group 2A (alkaline earth) metals, and aluminum will always form only one type of ion (Figure 4.14). Most of the transition metals will form more fhan one type of ion. Once you have identified the type of ionic compound, name if according to fhe scheme in fhe chart. If the ionic compound contains a polyatomic ion—something you must learn to recognize by familiarity—insert the name of the polyatomic ion in place of the metal (positive polyatomic ion) or the nonmetal (negative polyatomic ion). 

Find the total number of electrons available for bonding (valence electrons). If the structure is to represent a positive or negative polyatomic ion, the ion charge must be subtracted or added, respectively. 

Polar molecule A molecule in which there is a separation of charge and hence positive and negative poles, 183-185 dipole force, 237 orientation, 183 Polarimeter, 600 Polarity, 184-185 Pollutants, 6 Polyamide, 615-616 Polyatomic ion, 36,39 Polyatomic molecules, 654 Polyester A large molecule made up of ester units, 614-615 Polyethylene, 611-612... 

Ionic compounds are made up of positively charged ions (usually metal ions) and negatively charged ions (usually non-metal ions or polyatomic anions) held together by electrostatic forces of attraction. Molecular compounds are made up of discrete units called molecules. Generally they consist of a small number of nonmetal atoms held together by covalent bonds (sharing of electrons). 

Polar Molecule a molecule where the centers of positive and negative charge differ, creating a permanent dipole moment Polarizability ability of an electron cloud in a neutral atom to be distorted Polarized Light light in which the electromagnetic wave vibrates in only one plane Polyatomic Ion an ion consisting of more than one atom... 

Notice in Table 6-1 that all the common polyatomic ions except ammonium have a negative charge ranging between -1 and -3. You also see a number of -ite/-ate pairs, such as chlorite and chlorate, phosphite and phosphate, and nitrite and nitrate. If you look closely at these pairs, you notice that the only difference between them is the number of oxygen atoms in each ion. Specifically, the -ate ion always has one more oxygen atom than the -ite ion but has the same overall charge. 

Ionic compounds consist of positive ions (cations) and negative ions (anions) hence, ionic compounds often consist of a metal and nonmetal. The electrostatic attraction between a cation and anion results in an ionic bond that results in compound formation. Binary ionic compounds form from two elements. Sodium chloride (NaCl) and sodium fluoride (NaF) are examples of binary ionic compounds. Three elements can form ternary ionic compounds. Ternary compounds result when polyatomic ions such as carbonate (C032 ), hydroxide (OH-), ammonium (NH4+), form compounds. For example, a calcium ion, Ca2+, combines with the carbonate ion to form the ternary ionic compound calcium carbonate, CaC03. Molecular compounds form discrete molecular units and often consist of a combination of two nonmetals. Compounds such as water (H20), carbon dioxide (C02), and nitric oxide (NO) represent simple binary molecular compounds. Ternary molecular compounds contain three elements. Glucose ( 12 ) is a ternary molecular compound. There are several distinct differences between ionic and molecular compounds, as summarized in Table 1.2. 

Compounds containing polyatomic ions follow similar rules. In sodium carbonate, there are two Na+ ions per carbonate ion, so its formula is Na2C03. When a subscript has to be added to a polyatomic ion, the ion is written within parentheses, as in (NH4)2S04, where (NH4)2 means that there are two NH4+ (ammonium) ions for each S042- (sulfate) ion in ammonium sulfate. In each case, the ions combine in such a way that the positive and negative charges cancel all compounds are electrically neutral overall. 

However, a closer look shows that most of the reactions quoted are reactions of polyatomic ions, where it could be expected that the internal rotational and vibrational structures of the reactant ions and the activated complex will make a significant contribution. Values of gas phase A (Table 4.4) become increasingly more negative as the complexity of the reactants increases, with the corresponding calculated p factors likewise becoming increasingly smaller. This indicates that there cannot be a single point of comparison, and that there is considerable leeway in the value which can be chosen. 

To review Up to this point you have learned about the nomenclature of compounds formed from positive and negative ions of various kinds single ions, polyatomic ions, and multivalent ions. 

The negative ion of the acid can be a single element, as the Cl- in the example above, or it can be a polyatomic ion as shown in the equation below. The process is the same in either case. 

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