Write the Lewis structures for the following, and include resonance structures where appropriate. Indicate which has the strongest carbon-oxygen bond. (a) \(\mathrm{CO}_{2}\) (b) \(\mathrm{CO}\)

Resonance structures are alternate ways of drawing the Lewis structure for a molecule where the placement of electrons can vary but the atom positions remain the same. Resonance occurs because in some molecules, electrons are delocalized, meaning they are not confined to a single bond or lone pair.

Considering the example of carbon monoxide (CO), the molecule exhibits resonance. One structural representation includes a triple bond between carbon and oxygen and a lone pair of electrons on each atom. The second resonance structure shows a double bond with a formal charge: carbon has a positive charge, while the oxygen atom has a negative charge. These differing structures do not represent different molecules but are instead a blended 'average' that describes the true, intermediate nature of the molecule's bonding.

In general, the real structure is a hybrid of the resonance forms, and this can have implications on the molecule's stability, reactivity and bond characteristics.

Bond strength, often gauged by the amount of energy required to break a bond, is a critical factor influencing molecular structure and properties. Generally, multiple bonds such as double or triple bonds are stronger than single bonds, as they involve more shared electrons, resulting in a greater electron density between the atoms.

In the case of CO and CO2, the triple bond in CO is stronger than the double bonds in CO2. This means that CO has a higher bond dissociation energy, making it less reactive under normal circumstances. The strength of bonds also impacts melting and boiling points, as well as many other chemical properties. Hence, understanding bond strength is essential for predicting the behavior of molecules in chemical reactions and in different states of matter.

The octet rule is a fundamental principle in chemistry that refers to the tendency of atoms to prefer having eight electrons in their valence shell—the outermost electron shell. By attaining a full valence shell, atoms achieve a stable electronic configuration similar to that of the noble gases.

When atoms come together to form molecules, they do so in a way that allows each atom to achieve an octet. In CO2, carbon shares four valence electrons with two oxygen atoms, forming double bonds and satisfying the octet rule for all involved atoms. In CO, the octet rule is fulfilled by the carbon and oxygen through a triple bond and the presence of lone electron pairs.

There are exceptions to the octet rule, especially with elements that have d-orbitals and can accommodate more than eight electrons. However, for many common elements, including carbon and oxygen, the octet rule is highly instructive when predicting and understanding the possible structures and chemical behavior of molecules.