At this point, both terminal oxygen atoms have octets of electrons. We therefore place the last 2 electrons on the central atom:. The central oxygen has only 6 electrons.
We must convert one lone pair on a terminal oxygen atom to a bonding pair of electrons—but which one? Depending on which one we choose, we obtain either. Which is correct? In fact, neither is correct. As you will learn, if the bonds were of different types one single and one double, for example , they would have different lengths. It turns out, however, that both O—O bond distances are identical, Equivalent Lewis dot structures, such as those of ozone, are called resonance structures.
The position of the atoms is the same in the various resonance structures of a compound, but the position of the electrons is different. Double-headed arrows link the different resonance structures of a compound:. The double-headed arrow indicates that the actual electronic structure is an average of those shown, not that the molecule oscillates between the two structures.
When it is possible to write more than one equivalent resonance structure for a molecule or ion, the actual structure is the average of the resonance structures. Like ozone, the electronic structure of the carbonate ion cannot be described by a single Lewis electron structure. Because carbon is the least electronegative element, we place it in the central position:. Six electrons are used to form three bonding pairs between the oxygen atoms and the carbon:. At this point, the carbon atom has only 6 valence electrons, so we must take one lone pair from an oxygen and use it to form a carbon—oxygen double bond.
In this case, however, there are three possible choices:. As with ozone, none of these structures describes the bonding exactly. Each predicts one carbon—oxygen double bond and two carbon—oxygen single bonds, but experimentally all C—O bond lengths are identical. We can write resonance structures in this case, three of them for the carbonate ion:. Benzene is a common organic solvent that was previously used in gasoline; it is no longer used for this purpose, however, because it is now known to be a carcinogen.
Use resonance structures to describe the bonding in benzene. Given: molecular formula and molecular geometry. If we place a single bonding electron pair between each pair of carbon atoms and between each carbon and a hydrogen atom, we obtain the following:. B If the 6 remaining electrons are uniformly distributed pairwise on alternate carbon atoms, we obtain the following:.
C There are, however, two ways to do this:. Each structure has alternating double and single bonds, but experimentation shows that each carbon—carbon bond in benzene is identical, with bond lengths We can describe the bonding in benzene using the two resonance structures, but the actual electronic structure is an average of the two. The existence of multiple resonance structures for aromatic hydrocarbons like benzene is often indicated by drawing either a circle or dashed lines inside the hexagon:.
The sodium salt of nitrite is used to relieve muscle spasms. Resonance structures are particularly common in oxoanions of the p -block elements, such as sulfate and phosphate, and in aromatic hydrocarbons, such as benzene and naphthalene. Following steps are required to draw the CO 3 2- lewis structure and they are explained in detail in this tutorial. Drawing correct lewis structure is important to draw resonance structures of CO 3 2- correctly.
Carbon is located at group 4 in the periodic table. So, carbon has four electrons in its valence shell. Oxygen is located at 6 th group. It has six electrons in valence shell. There are -2 charge on CO 3 2- ion. Therefore there are two more electrons which contribute to the valence electrons.
Total electron pairs are determined by dividing the number total valence electrons by two. For, CO 3 2- ion, Total pairs of electrons are To be the center atom, ability of having higher valance is important. Carbon has the more chance to be the center atom See the figure because carbon can show valance of 4.
Oxygen's highest valence is 2. So, now we can build a sketch of CO 3 2- ion. After, marking electron pairs on atoms, we should mark charges of each atom. Marking of charges are significant because it is used to determine the best lewis structure of the ion. In new structure, charges of atoms are reduced than previous structure. Now there are no charge on on one oxygen atom and the carbon atom.
Also, only two oxygen atoms have -1 negative charges. Now you understand this structure of CO 3 2- is more stable than previous structure. So, this structure has more chance to be the lewis structure of CO 3 2- ion.
In carbonate ion, there is two oxygen atoms which has -1 charge on each of them. Lewis Structure for CO 3 2- Carbonate ion Lewis structure of carbonate ion is drawn in this tutorial step by step.
Carbonate ion CO 3 2- Carbonate ion has a -2 charge.
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