Based on molecular orbital theory, is the molecule B_2 paramagnetic or diamagnetic?

• A. Paramagnetic
• B. Diamagnetic

Answer: (A)

Verified step by step guidance

1. Recall that molecular orbital (MO) theory explains the bonding in molecules by combining atomic orbitals to form molecular orbitals, which can be bonding, antibonding, or nonbonding.
2. Determine the total number of valence electrons in the B\_2 molecule. Each boron atom has 3 valence electrons, so B\_2 has a total of 6 valence electrons.
3. Fill the molecular orbitals in order of increasing energy according to the MO diagram for B\_2. For B\_2, the order of orbitals is typically: \(\sigma_{2s}\), \(\sigma^*_{2s}\), \(\pi_{2p_x} = \pi_{2p_y}\), \(\sigma_{2p_z}\), and their corresponding antibonding orbitals.
4. Place the 6 valence electrons into these molecular orbitals following the Pauli exclusion principle and Hund's rule. Note that the two electrons in the degenerate \(\pi_{2p_x}\) and \(\pi_{2p_y}\) orbitals will occupy separate orbitals with parallel spins.
5. Since there are unpaired electrons in the \(\pi\) molecular orbitals, B\_2 is paramagnetic, meaning it is attracted to a magnetic field due to these unpaired electrons.