Ch.9 - Molecular Geometry and Bonding Theories

Brown - Chemistry: The Central Science 14th Edition

Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232당신이 사용하는 게 아니라요?교과서 변경

Brown 14th Edition

Ch.9 - Molecular Geometry and Bonding Theories

문제 111d

9장, 문제 111d

Carbon monoxide, CO, is isoelectronic to N2. (d) Would you expect the p2p MOs of CO to have equal atomic orbital contributions from the C and O atoms? If not, which atom would have the greater contribution?

검증된 단계별 안내

Understand the term 'isoelectronic': Isoelectronic species have the same number of electrons. Carbon monoxide (CO) and nitrogen (N2) both have 14 electrons, making them isoelectronic.

Consider the atomic structure of CO: Carbon (C) has an atomic number of 6 and oxygen (O) has an atomic number of 8. This means oxygen is more electronegative than carbon.

Analyze the effect of electronegativity on molecular orbitals (MOs): Electronegativity affects the distribution of electrons in molecular orbitals. The more electronegative atom tends to attract more electron density.

Apply the concept to CO: In the case of CO, since oxygen is more electronegative than carbon, the atomic orbitals of oxygen will contribute more to the molecular orbitals, particularly those involving electron density near the oxygen atom.

Conclude on the p2p MOs of CO: Given the higher electronegativity of oxygen, the p2p (pi 2p) molecular orbitals of CO would likely have a greater atomic orbital contribution from the oxygen atom than from the carbon atom.

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주요 개념

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Isoelectronic Species

Isoelectronic species are atoms, ions, or molecules that have the same number of electrons and, therefore, the same electronic structure. In this case, carbon monoxide (CO) and nitrogen gas (N2) both have 14 electrons, making them isoelectronic. Understanding this concept helps in predicting similarities in bonding and molecular orbital characteristics between different species.

Molecular Orbitals (MOs)

Molecular orbitals are formed by the linear combination of atomic orbitals (LCAO) when atoms bond together. In CO, the p2p molecular orbitals are derived from the p orbitals of carbon and oxygen. The contributions of each atom's atomic orbitals to the molecular orbitals can vary based on their electronegativity and atomic size, influencing the overall bonding characteristics.

Electronegativity and Atomic Size

Electronegativity is a measure of an atom's ability to attract and hold onto electrons, while atomic size refers to the distance from the nucleus to the outermost electrons. In CO, oxygen is more electronegative than carbon, which means that the p2p molecular orbitals will have a greater contribution from the oxygen atom. This difference affects the distribution of electron density and the overall stability of the molecule.

관련 실천

교과서 질문

a) Using only the valence atomic orbitals of a hydrogen atom and a fluorine atom, and following the model of Figure 9.46, how many MOs would you expect for the HF molecule?

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교과서 질문

(c) It turns out that the difference in energies between the valence atomic orbitals of H and F are sufficiently different that we can neglect the interaction of the 1s orbital of hydrogen with the 2s orbital of fluorine.

The 1s orbital of hydrogen will mix only with one 2p orbital of fluorine. Draw pictures showing the proper orientation of all three 2p orbitals on F interacting with a 1s orbital on H. Which of the 2p orbitals can actually make a bond with a 1s orbital, assuming that the atoms lie on the z-axis?

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교과서 질문

The energy-level diagram in Figure 9.36 shows that the sideways overlap of a pair of p orbitals produces two molecular orbitals, one bonding and one antibonding. In ethylene there is a pair of electrons in the bonding π orbital between the two carbons. Absorption of a photon of the appropriate wavelength can result in promotion of one of the bonding electrons from the p2p to the p*2p molecular orbital. (b) Assuming this electronic transition corresponds to the HOMO-LUMO transition, what is the LUMO in ethylene?

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교과서 질문

(b) How many of the MOs from part (a) would be occupied by electrons?

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교과서 질문

The energy-level diagram in Figure 9.36 shows that the sideways overlap of a pair of p orbitals produces two molecular orbitals, one bonding and one antibonding. In ethylene there is a pair of electrons in the bonding π orbital between the two carbons. Absorption of a photon of the appropriate wavelength can result in promotion of one of the bonding electrons from the p2p to the p*2p molecular orbital. (a) Assuming this electronic transition corresponds to the HOMO-LUMO transition, what is the HOMO in ethylene?

546

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교과서 질문

The energy-level diagram in Figure 9.36 shows that the sideways overlap of a pair of p orbitals produces two molecular orbitals, one bonding and one antibonding. In ethylene there is a pair of electrons in the bonding π orbital between the two carbons. Absorption of a photon of the appropriate wavelength can result in promotion of one of the bonding electrons from the p2p to the p*2p molecular orbital. (c) Is the C¬C bond in ethylene stronger or weaker in the excited state than in the ground state? Why?

510

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