Adhering to Electron Rules

Counting the number of donating or accepting electrons between metal atoms and ligand molecules can help you quickly learn to predict the stabilities, shapes, and structures of thousands of different organometallic compounds based on some simple calculations. 

All the electron counting rules are used to determine how many electrons are required to make a stable compound. To achieve stability, the outer shell of an atom should have no vacant sites where electrons can go in other words, it should have no free valence electrons, at which point it becomes stable and inert. When this occurs, the atom has the same electronic configuration as the next highest noble gas, and so becomes stable in a similar way to how the noble atoms are stable and inert. 

All atoms in the periodic table, with the exception of the noble gasses, have some amount of reactivity associated with them. The reactivity occurs due to 

A great deal has been discovered about the exact structures of organometallics because the restrictions on the number of electrons around the metal center affords a high degree of control. For example, the precision to which chiral catalysis can be predicted and carried out is possible because no complex is possible, or stable, if it breaks the electron counting rules. (Chiral catalysis is discussed further in Chapter 16.) 

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