The Lewis structure for allene is Make a sketch of the structure of this molecule that is analogous to Figure \(9.25 .\) In addition, answer the following three questions: (a) Is the molecule planar? (b) Does it have a nonzero dipole moment? (c) Would the bonding in allene be described as delocalized? Explain.

In order to draw the Lewis structure for allene, we first need to count the total number of valence electrons available for bonding. Allene has three carbon atoms and four hydrogen atoms. The valence electrons for each carbon atom are 4, and the valence electrons for each hydrogen atom are 1. So, the total number of valence electrons in allene is: (3 Carbon atoms x 4 valence electrons) + (4 Hydrogen atoms x 1 valence electron) = 12 + 4 = 16 valence electrons

Next, we will create the basic skeletal structure of allene by connecting the atoms with single bonds (2 electrons per bond). The central carbon atom is bonded with the two other carbon atoms, and each terminal carbon atom is bonded to two hydrogen atoms. - C = C = C - Each hydrogen atom is connected to one terminal carbon atom.

Now, we need to complete the octets of all the atoms in the structure by adding the remaining valence electrons as lone pairs. Place the remaining 8 electrons (16 - 8 = 8) around the carbon atoms to give them a complete octet. C=C=C Each carbon atom has a complete octet, and the hydrogen atoms satisfied with the two electrons they share with the carbon atoms. The Lewis structure for allene is now complete. Now that we have the Lewis structure, we can sketch the allene molecule and answer the three questions.

Based on the Lewis structure and according to the Figure 9.25 style, we can draw the allene molecule like this: H \ C = C = C \ H

(a) Is the molecule planar? No, the molecule is not planar. The two carbon atoms at the terminal ends and the hydrogen atoms attached to them form two perpendicular planes intersecting at the central carbon, forming a non-planar allene molecule. (b) Does it have a nonzero dipole moment? No, allene does not have a nonzero dipole moment. Allene is symmetric, meaning that the dipole moment vectors caused by the carbon-hydrogen and carbon-carbon bonds cancel each other out, resulting in a net dipole moment of zero. (c) Would the bonding in allene be described as delocalized? Explain. No, the bonding in allene cannot be described as delocalized. In allene, the electrons are localized in the carbon-carbon double bonds and carbon-hydrogen single bonds. In a delocalized bonding system, electrons are shared and spread out across multiple bonded atoms. This occurs in molecules like benzene where electrons are distributed over more than two atoms. Allene does not have such a bonding system, indicating that its bonding is not delocalized.