Electronegativity and oxidation numbers

Strategy The structure can be obtained by removing an oxygen atom from H O, (Figure 21.8). Relative acid strengths can be predicted on the basis of the electronegativity and oxidation number of the central nonmetal atom, following the rules cited above. 

How does the strength of an oxoacid depend on the electronegativity and oxidation number of the central atom ... 

Electronegativity and Oxidation Number An important use of electronegativity is in determining an atom s oxidation number (ON. see Section 4.5) ... 

The tetrafluoroammonium cation (NF/) has high electronegativity (the oxidation number of nitrogen is + 5) and high kinetic stability (NF4+ is isoelectronic with CF4).15 -17 It has been shown that in anhydrous hydrogen fluoride, benzene and its derivatives are fluorinated by tetrafluoroammonium tetrafluoroborate with substitution of hydrogen by fluorine.15-17... 

The value given in the table refer to the common oxidation states of the elements. For some elements variation of tin electronegativity with oxidation number is observed for example, FeXI I.a FeIn 1.9 Cux 1.9, Cu11 2.0 8nn 1.8, SnIV 1.9. For other elements see W. Gordy and W. J. O. Thomas. J. CA m. Phyt. 24. 439 (1036). 

IR-5.4.1 Order of citation of electropositive and electronegative constituents IR-5.4.2 Indication of proportions of constituents IR-5.4.2.1 Use of multiplicative prefixes IR-5.4.2.2 Use of charge and oxidation numbers... 

Strategy In each group, compare the electronegativities or oxidation numbers of the central atoms to determine which O—H bonds are the most polar. The more polar the O—H bond, the more readily it is broken and the stronger the acid. 

Figure 14 Lewis-Langmuir atomic charges. Top examples using the simplest formulation. Middle plot of the electronegativity ratio that interpolates between fonnal charge and oxidation number. The dotted line is the formal charge limit and (0,0) is the oxidation number limit. Bottom improved LLa formula that corrects for charge on nearest neighbor atom...

Most of the time we are concerned only with whether a particular reaction is an oxidation or reduction rather than with detenrrining the precise change in oxidation number. In general Oxidation of carbon occurs when a bond between carbon and an atom that is less electronegative than carbon is replaced by a bond to an atom that is more electronegative than carbon. The reverse process is reduction. 

Notice that this generalization follows naturally from the method of calculating oxidation numbers outlined in Table 2.5. In a C—C bond one electron is assigned to one carbon, the second electron to the other. In a bond between carbon and some other element, none of the electrons in that bond ar e assigned to car bon when the element is more electronegative than carbon both are assigned to carbon when the element is less electronegative than carbon. 

Fluorine has a number of peculiarities that stem from its high electronegativity, small size, and lack of available d-orbitals. It is the most electronegative element of all and has an oxidation number of — 1 in all its compounds. Its high electronegativity and small size allow it to oxidize other elements to their highest oxidation numbers. The small size helps in this, because it allows several F atoms to pack around a central atom, as in IF7. 

The bonding electrons in CO and CO2 are polarized in the direction of the O atoms, as shown by the electronegativities of C (2.5) and O (3.5). Thus, if these substances were ionic, CO would consist of C cations and O anions, and CO2 would contain cations and O anions. Accordingly, we assign O an oxidation number of-2 in both these compounds, whereas C has an oxidation number of +2 in CO and +4 in CO2. ... 

Since O is to the right of C in the second period of the periodic table, O is more electronegative, and we assign control of all eight shared electrons to the two O atoms. (It does not really have complete control of the electrons if it did, the compound would be ionic.) Thus, the oxidation number of each atom is calculated as follows ... 

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