Questions:
1. How many sigma (σ) and pi (π) bonds are in each of the following molecules?
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Molecule
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Number of σ bonds
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Number of π bonds
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Molecule
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Number of σ bonds
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Number of π bonds
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CO2
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XeF3+
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|
|
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N2
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|
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Cl2CO
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|
|
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CO32- ion
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|
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BrO3_
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|
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2. An iron atom is located in a molecule called an "iron-porphyrin" (or "heme") which has an important role for the function of hemoglobin in the blood. The iron atom in hemoglobin is the place where the oxygen molecule (O2) is carried and taken to all the cells in our bodies for cellular metabolism. Before the oxygen gas bonds to the iron, the iron atom has a particular geometry of bonding domains: four nitrogen atoms from the porphyrin molecule are bonded to the iron atom and a fifth nitrogen atom from the hemoglobin molecule is also bonded to the iron. When the oxygen gas molecule bonds to the iron, it forms the sixth bonding domain to iron.
(a) What is the likely hybridization of the bonds around the central iron atom before the oxygen gas molecule bonds to the iron? Explain your answer in one or two sentences.
(b) What is the likely hybridization of the bonds around the central iron atom after the oxygen gas molecule bonds to the iron? Explain your answer in one or two sentences.
(c) Some years ago scientists obtained experimental data that appeared to indicate that the geometry around the iron atom in a porphyrin might be the same before and after bonding of the oxygen gas. Because of this data, some scientists argued that a water molecule might be attached to the iron atom and then is displaced by the oxygen molecule. If this was true, what would you predict the geometry to be around the iron atom in the porphyrin? Explain in one or two sentences how this evidence might affect what you answered above.