Understanding the Magnetic Behavior of Oxygen Molecule

The question asks about the magnetic properties exhibited by the oxygen molecule ($\text{O}_2$). Substances can be classified based on how they interact with a magnetic field. This interaction is related to the presence or absence of unpaired electrons in their atomic or molecular structure.

To determine the magnetic property of a molecule like the Oxygen molecule, we use the Molecular Orbital Theory (MOT). MOT explains chemical bonding and molecular properties by considering the combination of atomic orbitals to form molecular orbitals.

Molecular Orbital Diagram for Oxygen Molecule ($\text{O}_2$)

An oxygen atom ($\text{O}$) has an atomic number of 8, with an electron configuration of $1s^2 2s^2 2p^4$. The valence electrons are in the $2s$ and $2p$ orbitals (6 valence electrons per oxygen atom). Therefore, the $\text{O}_2$ molecule has a total of $6 + 6 = 12$ valence electrons.

According to Molecular Orbital Theory, atomic orbitals combine to form bonding and antibonding molecular orbitals. For second-period diatomic molecules like $\text{O}_2$, the order of filling molecular orbitals is generally:

$\sigma_{2s}, \sigma^*_{2s}, \sigma_{2p_z}, (\pi_{2p_x} = \pi_{2p_y}), (\pi^*_{2p_x} = \pi^*_{2p_y}), \sigma^*_{2p_z}$

However, for $\text{O}_2$ and $\text{F}_2$, there is a slight change in the order: the $\sigma_{2p_z}$ orbital is higher in energy than the $\pi_{2p}$ orbitals.

The corrected order for $\text{O}_2$ is:

$\sigma_{2s}, \sigma^*_{2s}, (\pi_{2p_x} = \pi_{2p_y}), \sigma_{2p_z}, (\pi^*_{2p_x} = \pi^*_{2p_y}), \sigma^*_{2p_z}$

Now, let's fill the 12 valence electrons into these molecular orbitals following Hund's rule and the Aufbau principle:

• $\sigma_{2s}^2$ (2 electrons)
• $\sigma^*_{2s}^2$ (4 electrons)
• $\pi_{2p_x}^2, \pi_{2p_y}^2$ (8 electrons)
• $\sigma_{2p_z}^2$ (10 electrons)
• $\pi^*_{2p_x}^1, \pi^*_{2p_y}^1$ (12 electrons)

The electron configuration for the $\text{O}_2$ molecule is $\sigma_{2s}^2 \sigma^*_{2s}^2 \sigma_{2p_z}^2 \pi_{2p_x}^2 \pi_{2p_y}^2 \pi^*_{2p_x}^1 \pi^*_{2p_y}^1$.

Identifying Unpaired Electrons and Magnetic Properties

Looking at the electron configuration, we see that the antibonding $\pi^*$ molecular orbitals ($\pi^*_{2p_x}$ and $\pi^*_{2p_y}$) each contain one electron. These are unpaired electrons.

The presence of unpaired electrons in a substance is responsible for its magnetic behavior. Let's look at the different types of magnetism mentioned in the options:

• Diamagnetism: Substances that are weakly repelled by a magnetic field. They have no unpaired electrons (all electrons are paired).
• Paramagnetism: Substances that are weakly attracted by a magnetic field. They contain one or more unpaired electrons.
• Ferromagnetism: Substances that are strongly attracted by a magnetic field and can retain their magnetism after the external field is removed. They have unpaired electrons that align strongly with each other in domains.
• Antiferromagnetism: Substances where neighboring unpaired electrons align in opposite directions, resulting in no net magnetic moment.

Since the Oxygen molecule ($\text{O}_2$) has two unpaired electrons in its antibonding $\pi^*$ molecular orbitals, it is attracted to a magnetic field. This property is known as Paramagnetism.

This prediction from Molecular Orbital Theory is consistent with experimental observations, which confirm that the Oxygen molecule is paramagnetic.

Therefore, the oxygen molecule exhibits Paramagnetism.