Nitric acid formal charges

Moving now to nitrogen we see that it has four covalent bonds (two single bonds + one double bond) and so its electron count is 5(8) = 4 A neutral nitrogen has five electrons m its valence shell The electron count for nitrogen m nitric acid is one less than that of a neutral nitrogen atom so its formal charge is +1... 

Like nitric acid each of the following inorganic compounds will be frequently encountered in this text Calculate the formal charge on each of the atoms in the Lewis structures given... 

Electron Delocalization in the Conjugate Base With a of —1 4 nitnc acid is almost completely ionized m water If we look at the Lewis structure of nitric acid m light of what we have said about inductive effects we can see why The N atom m nitric acid IS not only electronegative m its own right but bears a formal charge of +1 which enhances its ability to attract electrons away from the —OH group... 

Just as mild oxidation converts thiols to disulfides, vigorous oxidation converts them to sulfonic acids. KMn04 or nitric acid (HN03), or even bleach (NaOCl), can be used as the oxidant for this reaction. Any Lewis structure of a sulfonic acid requires either separation of formal charges or more than 8 electrons around sulfur. Sulfur can have an expanded octet, as it does in SF4 (10 electrons) and SF6 (12 electrons). The three resonance forms shown here are most commonly used. Organic chemists tend to use the form with an expanded octet, and inorganic chemists tend to use the forms with charge separation. 

As normally written nitric acid involves two N-O double bonds, in which the N atom has an octet expanded from eight to ten, which is unusual for a first short period element. However, the alternative of one N = 0 and one N -0 bond involves a difference of 2 in the formal charge of the latter, and consequently the former structure is preferred. 

Nitric acid, which exists as HNO3 molecules in the absence of water, has the skeletal structure shown. Show the important resonance structures of HNO3, and designate the formal charges on each atom. 

Many of the compounds can be regarded as derived from a basic polymerised phosphorus network in which a few of the P atoms are linked to 2 rather than to 3 other P atoms. The formal negative charges so introduced have to be balanced by a suitable number of cations added to the structure. Unlike K3P which is easily hydrolysed, KPjj is digested only by nitric acid and bromine. 

Example 2 Calculate the formal charges of the atoms In nitric acid. 

The N atom in nitric acid has four covalent bonds, thereby exceeding its normal covalency of three. The N atom also bears a formal charge. These circumstances are related. Invariably, an atom with an octet of electrons will have a formal charge when not exhibiting its normal covalency. (See Problem 8, page 143.)... 

A topic for next chapter The -1 formal charge of nitric acid is not localized" on O, so it is not a strong base ... 

Scheme 6.93. The formation of the nitronium ion (NO2 ) from nitric (HONO2) and snlfuric (H2SO4) acids in the presence of methylbenzene (tolnene [C6HSCH3]) and the snbseqnent reaction of N02" to prodnce l-methyl-2-nitrobenzene (orf/jo-nitrotolnene), l-methyl-4-nitrobenzene (para-nitrotolnene), and l-methyl-3-nitrobenzene (mefa-nitrotolnene). Using the curved arrow to indicate the movement of a pair of electrons (as nsual) there is a resonance form in which the positive charge is formally placed on the ring carbon bearing the methyl (CH3-) group for the first two. No such form can be written for the last.

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