Page 149 - Arrow Pushing in Inorganic Chemistry A Logical Approach to the Chemistry of the Main Group Elements

5A

Nitrogen

Brot aus Luft (Bread out of air)
Fritz Haber, Referring to his discovery of the industrial synthesis of ammonia.

Nitrogen, in many ways, is a paradigm of a lighter p-block element. In other words, it
embodies a wide range of properties that we typically associate with the upper part of
the p block: multiple valence states, a range of oxidation states, both electrophilic and
nucleophilic behavior in its different compounds, an ability to form strong bonds with many
different elements, and an extensive capacity for multiple bonding. In addition, the most
familiar nitrogen compounds, such as oxides, oxoacids, hydrides, and halides, engage in
some of the most mechanistically interesting reactions that we will encounter in this book.
Nitrogen is also one of the key elements of organic chemistry. These considerations led us to
dedicate a separate chapter to nitrogen, a distinction that we have not accorded to any other
element in this book. A good grounding in nitrogen chemistry is not only worthwhile on its
own merits, but it also affords a better appreciation of the distinctive features of the heavier
p-block elements. A few broad generalizations on nitrogen chemistry are as follows.

2
• With a 2s 2p 3 valence configuration, nitrogen exhibits two common valence
states—tri- and penta-valent. Examples of trivalent nitrogen include NH ,N , and
3
2
–
NO ; examples of the pentavalent state include NH 4 + and HNO .Asafirst-row
2
3
(period 2) element, nitrogen generally cannot accommodate more than four bonds,
so the equation
valence = number of bonds + formal charge
implies that pentavalent nitrogen atoms must carry a formal charge of at least +1;
indeed, a +1 formal charge is common for pentavalent nitrogen.
• The Pauling electronegativity of nitrogen (3.04) is one of the highest, after fluorine
(3.98) and oxygen (3.44), and about the same as chlorine (3.16). Nitrogen is much
more electronegative than the other group 15 elements (the Pauling electronegativities

Arrow Pushing in Inorganic Chemistry: A Logical Approach to the Chemistry of the Main-Group Elements,
First Edition. Abhik Ghosh and Steffen Berg.
© 2014 John Wiley & Sons, Inc. Published 2014 by John Wiley & Sons, Inc.

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