Is C2 2 Paramagnetic Or Diamagnetic

Is C₂²⁻ Paramagnetic or Diamagnetic? Understanding Molecular Orbital Theory

Determining whether a molecule is paramagnetic or diamagnetic hinges on understanding its electronic configuration, specifically the presence of unpaired electrons. This article will explore the molecular orbital diagram of the C₂²⁻ ion to definitively answer whether it's paramagnetic or diamagnetic. We'll delve into the intricacies of molecular orbital theory and explain the process clearly and concisely.

The key to understanding the magnetic properties of C₂²⁻ lies in constructing its molecular orbital diagram. This diagram illustrates how atomic orbitals combine to form molecular orbitals, and how electrons fill these orbitals according to Hund's rule and the Aufbau principle.

Understanding Molecular Orbital Theory and Magnetic Properties

Molecular orbital (MO) theory describes the behavior of electrons in molecules. In essence, atomic orbitals combine to form molecular orbitals, which can be either bonding (lower in energy) or antibonding (higher in energy). Electrons fill these orbitals from the lowest energy level upwards.

A molecule is considered diamagnetic if all its electrons are paired, meaning they occupy orbitals in pairs with opposite spins. Diamagnetic substances are weakly repelled by magnetic fields. Conversely, a molecule is paramagnetic if it possesses one or more unpaired electrons. Paramagnetic substances are attracted to magnetic fields.

Constructing the Molecular Orbital Diagram for C₂²⁻

Carbon has six electrons. Therefore, two carbon atoms contribute 12 electrons. The 2- charge adds two more electrons, giving us a total of 14 electrons to place in the molecular orbitals of C₂²⁻. The order of energy levels for the molecular orbitals of C₂ is σ2s < σ2s < σ2p < π2p < π2p < σ*2p.

Following the Aufbau principle and Hund's rule:

1. σ2s and σ*2s: The two lowest energy orbitals are filled with four electrons (two pairs).
2. σ2p: The next lowest energy orbital is filled with two electrons (one pair).
3. π2p: The two degenerate π2p orbitals are filled with four electrons (two pairs).
4. π2p and σ2p: The remaining four electrons fill the π*2p orbitals, two electrons in each of the two degenerate orbitals resulting in two pairs of electrons

Therefore, the molecular orbital diagram shows that all 14 electrons in C₂²⁻ are paired.

Conclusion: C₂²⁻ is Diamagnetic

Because all electrons in the C₂²⁻ molecular orbital diagram are paired, there are no unpaired electrons. This means that the C₂²⁻ ion is diamagnetic. It will be weakly repelled by a magnetic field.

This explanation clearly outlines the process of determining the magnetic properties of C₂²⁻ using molecular orbital theory. By systematically filling the molecular orbitals with electrons and examining for unpaired electrons, we conclusively determine the diamagnetic nature of this ion.