Formal Charge Compared To Oxidation State
The concept of oxidation states constitutes a competing method to assess the distribution of electrons in molecules. If the formal charges and oxidation states of the atoms in carbon dioxide are compared, the following values are arrived at:
The reason for the difference between these values is that formal charges and oxidation states represent fundamentally different ways of looking at the distribution of electrons amongst the atoms in the molecule. With formal charge, the electrons in each covalent bond are assumed to be split exactly evenly between the two atoms in the bond (hence the dividing by two in the method described above). The formal charge view of the CO2 molecule is essentially shown below:
The covalent (sharing) aspect of the bonding is overemphasized in the use of formal charges, since in reality there is a higher electron density around the oxygen atoms due to their higher electronegativity compared to the carbon atom. This can be most effectively visualized in an electrostatic potential map.
With the oxidation state formalism, the electrons in the bonds are "awarded" to the atom with the greater electronegativity. The oxidation state view of the CO2 molecule is shown below:
Oxidation states overemphasize the ionic nature of the bonding; most chemists agree that the difference in electronegativity between carbon and oxygen is insufficient to regard the bonds as being ionic in nature.
In reality, the distribution of electrons in the molecule lies somewhere between these two extremes. The inadequacy of the simple Lewis structure view of molecules led to the development of the more generally applicable and accurate valence bond theory of Slater, Pauling, et al., and henceforth the molecular orbital theory developed by Mulliken and Hund.
Read more about this topic: Formal Charge
Famous quotes containing the words formal, charge, compared and/or state:
“The spiritual kinship between Lincoln and Whitman was founded upon their Americanism, their essential Westernism. Whitman had grown up without much formal education; Lincoln had scarcely any education. One had become the notable poet of the day; one the orator of the Gettsyburg Address. It was inevitable that Whitman as a poet should turn with a feeling of kinship to Lincoln, and even without any association or contact feel that Lincoln was his.”
—Edgar Lee Masters (1869–1950)
“I do the wrong, and first begin to brawl.
The secret mischiefs that I set abroach
I lay unto the grievous charge of others.”
—William Shakespeare (1564–1616)
“Brute force crushes many plants. Yet the plants rise again. The Pyramids will not last a moment compared with the daisy. And before Buddha or Jesus spoke the nightingale sang, and long after the words of Jesus and Buddha are gone into oblivion the nightingale still will sing. Because it is neither preaching nor commanding nor urging. It is just singing. And in the beginning was not a Word, but a chirrup.”
—D.H. (David Herbert)
“Thus we steadily worship Mammon, both school and state and church, and on the seventh day curse God with a tintamar from one end of the Union to the other.”
—Henry David Thoreau (1817–1862)