Electronegativity multiple-bond

On the other hand, groups that have a multiple-bonded electronegative atom directly connected to an unsaturated system are —A/ groups. In such cases, we can draw canonical forms in which electrons have been taken from the unsaturated system into the group, for example. 

Multiple bonds between atoms with different electronegativities such as the C=0 and S=0 bonds, are also necessarily polar. This polarity is frequently represented by resonance structures such as... 

The elements in groups 15-18 in period 3 and beyond also form multiple bonds with each other. But because these elements have smaller electronegativities than the corresponding elements of period 2, they are appreciably weaker than the multiple bonds between... 

The largest group of inorganic heteroatomic chain compounds with considerable industrial potential is the phosphazenes,18,23 which are based on a phosphorus-nitrogen skeleton. The electronegativity difference here (xp = 2.19, xn = 3.04) is less than in the siloxane link, but some multiple bonding is involved between N and P, which strengthens the framework. The... 

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