Next page chemical bond

You can use electronegativity differences to think of chemical bonds as having a percent ionic or a percent covalent character. The graph below plots percent ionic character versus AEN for a number of gaseous binary molecules. Use this graph to answer the questions on the next page. 

For many molecules it is possible to formulate valence-bond structures that are so reasonable and that account so satisfactorily for the properties of the substances that they are accepted by everyone without hesitation. The structures given on the next page may be shown for illustration. The physical and chemical properties of substances and the configurations of molecules associated with structures of this type are well understood, and this understanding forms the basis for a large part of chemical reasoning. 

Ideally, the size of an atom is defined by the edge of its orbital. However, this boundary is fuzzy and varies under different conditions. Therefore, the conditions under which the atom exists must be specified to estimate its size. One way to express an atom s radius is to measme the distance between the nuclei of two identical atoms that are chemically bonded together and then divide this distance by two. Atomic radius may be defined as one-half the distance between the nuciei of identicai atoms that are bonded together. This can be seen in Figure 3.1 on the next page. 

Kekule structures are like Lewis structures except lone pairs are normally omitted. Structures are often further simplified by omitting some (or aU) of the covalent bonds and hsting atoms bonded to a particular carbon (or nitrogen or oxygen) next to it (with a subscript if there is more than one of a particular atom). Lone-pair electrons are usually not shown, unless they are needed to draw attention to some chemical property of the molecule. These structures are called condensed structures. Compare the condensed sttuctures shown here with the Lewis structures shown on page 17. 

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