Use the MO model to predict the structure of ketene (H2CCO). Draw a Lewis structure of the molecule that shows the positions of the orbitals and the atoms in three-dimensional perspective.

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To predict the structure of ketene (H2CCO) using the MO model, we need to follow these steps:

1. Determine the number of valence electrons. Ketene (H2CCO) consists of 2 hydrogen atoms, 2 carbon atoms, and 1 oxygen atom. Hydrogen has 1 valence electron, carbon has 4, and oxygen has 6. Therefore, the total number of valence electrons is 2 + 2(4) + 6 = 16.

2. Use the Lewis structure to determine the connectivity of the atoms. In ketene, the two carbon atoms are double-bonded to each other, and each carbon is singly bonded to a hydrogen atom. The oxygen atom is also doubly bonded to one of the carbon atoms, as shown below:

H H
\ /
C=C=O

3. Place the valence electrons around the atoms to satisfy the octet rule. Each hydrogen atom is connected to a carbon atom and therefore contributes 2 electrons to the bonding. The bond between the two carbon atoms consists of 4 shared electrons, and the double bond between carbon and oxygen also consists of 4 shared electrons. In total, we have 2 + 2(2) + 4 + 4 = 16 electrons, satisfying the octet rule for all atoms.

4. Draw the Lewis structure, keeping in mind that multiple resonance structures may exist due to the delocalization of electrons. The resulting Lewis structure for ketene is:

H H
\ /
:C=C=O:

5. Determine the positions of the orbitals and atoms in three-dimensional perspective. In ketene, each carbon atom possesses three sigma bonds (one to hydrogen, one to the other carbon, and one to oxygen), resulting in a trigonal planar geometry around each carbon atom. The oxygen atom, on the other hand, has two sigma bonds (one to carbon and one to one of the lone pairs), resulting in a linear geometry.

To summarize, the predicted structure of ketene (H2CCO) according to the MO model is a planar molecule with two carbon atoms connected by a double bond, and each carbon atom is bonded to a hydrogen atom. The oxygen atom is doubly bonded to one of the carbon atoms.