L-ewis structures

Self-Tkst 2.6A Write a L.ewis structure for the urea molecule, (NHj CD. 

U 3 Draw the l,ewis structures of molecules and ions (Toolbox... 

Select from each of the following pairs of l ewis structures the one that is likely to make the dominant contribution to a resonance hybrid. Explain your selection. ... 

Lewis s theory of the chemical bond was brilliant bul it was little more than guesswork inspired by insight. 1 ewis had no way of knowing why an electron pair, the essential feature of his approach, was so important. The valence-bond theory explained this point but could not explain the properties of some molecules. For example, the Lewis description of 02 is 0=0, with all the electrons paired. However, oxygen is a paramagnetic substance (Fig. 3.28 and Box 3.2), and paramagnetism is a property of unpaired electrons. The magnetism of O, therefore contradicts both the l wis structure and the valence-bond description of the molecule. 

Chlorine dioxide is an odd molecule that is, a molecule containing an odd number of electrons. It was pointed out by G. N. L.ewis in 19J6 that odd molecules (other than those containing transition elements) are rare, and that they are usually colored and are always paramagnetic (attracted by a magnet). Every electronic structure that can bjC written for chlorine dioxide contains one unpaired electron. This unpaired electron presumably resonates among the three atoms, the electronic structure of the molecule being a resonance hybrid ... 

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