Question

The transport of \(\mathrm{O}_{2}\) in the blood is carried out by hemoglobin. Carbon monoxide can interfere with oxygen transport because hemoglobin has a stronger affinity for \(\mathrm{CO}\) than for \(\mathrm{O}_{2}\). If \(\mathrm{CO}\) is present, normal uptake of \(\mathrm{O}_{2}\) is prevented, depriving the body of needed oxygen. Using the molecular orbital model, write the electron configurations for \(\mathrm{CO}\) and \(\mathrm{for} \mathrm{O}_{2}\). From your configurations, give two property differences between \(\mathrm{CO}\) and \(\mathrm{O}_{2}\).

Short answer

The electron configurations for CO and O₂ using the molecular orbital model are: CO: (σ₁s)²(σ*₁s)²(σ₂s)²(σ*₂s)²(σ₂pz)²(π₂px)²(π₂py)¹(π*₂px)¹(π*₂py)⁰(σ*₂pz)⁰ O₂: (σ₁s)²(σ*₁s)²(σ₂s)²(σ*₂s)²(σ₂pz)²(π₂px)²(π₂py)²(π*₂px)¹(π*₂py)¹(σ*₂pz)⁰ Two property differences between CO and O₂ are: 1. Bond order: CO has a triple bond (bond order of 1), indicating a stronger bond than O₂, which has a double bond (bond order of 2). 2. Magnetic properties: Both CO and O₂ are paramagnetic, but O₂ has a stronger paramagnetism due to having two unpaired electrons compared to only one in CO.

Step-by-step solution

Write electron configurations for CO and O₂

First, we need to write the electron configurations for CO and O₂ using the molecular orbital model. We need to find the atomic orbitals for each atom and then combine them to form molecular orbitals.

Identify atomic orbitals

For CO, the atomic orbitals for C and O need to be identified. For O₂, we need the atomic orbitals for O (oxygen). Carbon, C Atomic Orbitals: 1s² 2s² 2px² 2py¹ 2pz¹ Oxygen, O Atomic Orbitals: 1s² 2s² 2px² 2py¹ 2pz²

Combine atomic orbitals to form molecular orbitals for CO and O₂

Now let's combine these atomic orbitals to form molecular orbitals, keeping in mind the order of molecular orbitals: σ₁s, σ*₁s, σ₂s, σ*₂s, σ₂pz, π₂px=π₂py, π*₂px=π*₂py, and σ*₂pz. For σ₁s and σ*₁s levels, we always fill 2 electrons in both CO and O₂. So, we only need to consider the other orbital levels. CO molecular orbitals: - (σ₁s)² - (σ*₁s)² - (σ₂s)² - (σ*₂s)² - (σ₂pz)² - (π₂px)²(π₂py)¹ - (π*₂px)¹(π*₂py)⁰ - (σ*₂pz)⁰ O₂ molecular orbitals: - (σ₁s)² - (σ*₁s)² - (σ₂s)² - (σ*₂s)² - (σ₂pz)² - (π₂px)²(π₂py)² - (π*₂px)¹(π*₂py)¹ - (σ*₂pz)⁰

Identify two property differences between CO and O₂

1. Bond order: In CO, there are 6 bonding electrons (σ₁s, σ₂s, σ₂pz, π₂px) and 4 antibonding electrons (σ*₁s, σ*₂s, and π*₂px). The bond order is (6-4)/2 = 1. In O₂, there are 8 bonding electrons (σ₁s, σ₂s, σ₂pz, π₂px, and π₂py) and 4 antibonding electrons (σ*₁s, σ*₂s, π*₂px, and π*₂py). The bond order is (8-4)/2 = 2. Hence, CO has a triple bond and O₂ has a double bond. This suggests that CO has a stronger bond than O₂. 2. Magnetic properties: CO has an unpaired electron in the π*₂px molecular orbital, which makes it paramagnetic. O₂ also has unpaired electrons in the π*₂px and π*₂py molecular orbitals, making it paramagnetic as well. However, the presence of two unpaired electrons in O₂ implies a stronger paramagnetism as compared to CO with only one unpaired electron.

Key concepts

Electron Configuration

Understanding electron configuration is crucial when discussing molecular orbital models, especially with molecules like carbon monoxide (CO) and oxygen (O₂). The electron configuration helps us determine how electrons are distributed in the molecular orbitals of a molecule. It involves organizing electrons in specific orbitals that correspond to their energy levels.

For carbon monoxide (CO), combining the atomic orbitals of the carbon (C) and oxygen (O) atoms gives us molecular orbitals in which the electrons reside. Similarly, oxygen (O₂) involves the combination of atomic orbitals from two oxygen atoms to form its molecular orbitals. It's important to note that the molecular orbitals are formed in a sequence of increasing energy levels, usually starting from \( \sigma_{1s}, \sigma_{1s}^*, \sigma_{2s}, \sigma_{2s}^*, \sigma_{2p_z}, \pi_{2p_x} = \pi_{2p_y}, \pi_{2p_x}^* = \pi_{2p_y}^*, \sigma_{2p_z}^* \).

This ordering helps in writing the electron configuration for both CO and O₂, letting us visualize and understand how electrons are paired or unpaired in their respective molecules.

Carbon Monoxide

Carbon monoxide (CO) is a diatomic molecule composed of one carbon and one oxygen atom. Its molecular orbital configuration offers insights into its chemical properties. In CO, the molecular orbitals are filled with electrons in the following configuration:

• (\(\sigma_{1s}\))²
• (\(\sigma_{1s}^*\))²
• (\(\sigma_{2s}\))²
• (\(\sigma_{2s}^*\))²
• (\(\sigma_{2p_z}\))²
• (\(\pi_{2p_x}\))² (\(\pi_{2p_y}\))¹
• (\(\pi_{2p_x}^*\))¹
• (\(\sigma_{2p_z}^*\))⁰

This configuration shows that CO has a bond order of 3, indicating a triple bond between carbon and oxygen. The presence of a triple bond suggests a strong interaction between the two atoms. CO has one unpaired electron in its highest energy \(\pi_{2p_x}^*\) molecular orbital, contributing to its paramagnetic property.

Its strong bonding implies stability, but the paramagnetic nature can influence behavior in magnetic fields. Additionally, the affinity of CO for binding with hemoglobin showcases its reactivity compared to molecules like O₂ that support vital functions.

Oxygen

Oxygen (O₂) is essential for life and has unique chemical properties often explored through its electron configuration. In molecular orbital terms, O₂'s configuration looks like this:

• (\(\sigma_{1s}\))²
• (\(\sigma_{1s}^*\))²
• (\(\sigma_{2s}\))²
• (\(\sigma_{2s}^*\))²
• (\(\sigma_{2p_z}\))²
• (\(\pi_{2p_x}\))² (\(\pi_{2p_y}\))²
• (\(\pi_{2p_x}^*\))¹ (\(\pi_{2p_y}^*\))¹
• (\(\sigma_{2p_z}^*\))⁰

The bond order for O₂ is 2, indicating a double bond between the two oxygen atoms. This configuration involves two unpaired electrons, which is unusual and leads to O₂'s paramagnetic character. These unpaired electrons are present in the \(\pi_{2p_x}^*\) and \(\pi_{2p_y}^*\) orbitals, making O₂ quite different in its magnetic properties compared to other diatomic molecules.

Oxygen is critical for combustion and respiration, significantly impacting biological and chemical processes despite its paramagnetic nature, showcasing how electron configuration ties to physical and magnetic properties.

Paramagnetic Properties

Paramagnetism refers to the tendency of certain materials or molecules, like CO and O₂, to become magnetized in the presence of an external magnetic field. This occurs due to the presence of unpaired electrons in their molecular orbitals.

In the case of CO, the presence of a single unpaired electron in the \(\pi_{2p_x}^*\) orbital accounts for its paramagnetism. However, this property is relatively weak because there's only one unpaired electron.

Oxygen, on the other hand, has two unpaired electrons located in the \(\pi_{2p_x}^*\) and \(\pi_{2p_y}^*\) molecular orbitals. These lead to a stronger paramagnetic effect compared to CO. The spin of these electrons causes O₂ to be more strongly attracted to a magnetic field.

Understanding these paramagnetic properties is not just a matter of academic interest. It helps explain phenomena such as the behavior of oxygen in magnetic fields and its interactions at the molecular level, providing a deeper insight into everyday applications and biological functions.