Using the molecular orbital energy ordering for second-row homonuclear diatomic molecules in which the π2p orbitals lie at higher energy than the σ2p, draw MO energy diagrams and predict the bond order in a molecule or ion with 12 total valence electrons. Will the molecule or ion be diamagnetic or paramagnetic?

Verified step by step guidance

1. Identify the second-row homonuclear diatomic molecule or ion with 12 valence electrons. Examples include \( \text{C}_2 \) or \( \text{N}_2^+ \).
2. Write the electron configuration for the molecule using the molecular orbital (MO) theory. For second-row diatomic molecules, the order is: \( \sigma_{1s}^2, \sigma^*_{1s}^2, \sigma_{2s}^2, \sigma^*_{2s}^2, \pi_{2p_x}^2 = \pi_{2p_y}^2, \sigma_{2p_z}^2 \).
3. Fill the molecular orbitals with the 12 valence electrons according to the Aufbau principle, Pauli exclusion principle, and Hund's rule.
4. Calculate the bond order using the formula: \( \text{Bond Order} = \frac{1}{2}[(\text{Number of electrons in bonding MOs}) - (\text{Number of electrons in antibonding MOs})] \).
5. Determine if the molecule or ion is diamagnetic or paramagnetic by checking for unpaired electrons in the molecular orbitals. If all electrons are paired, it is diamagnetic; if there are unpaired electrons, it is paramagnetic.

Key Concepts

Molecular Orbital Theory

Molecular Orbital Theory describes how atomic orbitals combine to form molecular orbitals, which can be occupied by electrons. In diatomic molecules, these orbitals are arranged in energy levels, and their occupancy determines the molecule's properties, including bond order and magnetic behavior. Understanding the energy ordering of these orbitals is crucial for predicting the stability and characteristics of the molecule.

Bond Order

Bond order is a measure of the number of chemical bonds between a pair of atoms, calculated as half the difference between the number of bonding and antibonding electrons in a molecular orbital diagram. A higher bond order indicates a stronger bond and greater stability of the molecule. For a molecule with 12 valence electrons, determining the bond order involves filling the molecular orbitals according to their energy levels and counting the electrons appropriately.

Magnetism in Molecules

The magnetic properties of a molecule, whether it is diamagnetic or paramagnetic, depend on the presence of unpaired electrons in its molecular orbitals. Diamagnetic molecules have all electrons paired and are not attracted to a magnetic field, while paramagnetic molecules contain unpaired electrons and are attracted to magnetic fields. Analyzing the electron configuration from the molecular orbital diagram helps predict the magnetic behavior of the molecule or ion.