Question

The highest energy occupied molecular orbital in the b−b bond of the b2 molecule is _____

Answer 1

Π2py and Π2pz

Step-by-step explanation:

In the molecular orbital electron configuration of the boron molecule B2, the electrons are arranged as follows:

KK,σ2s^2,σ*2s^2, Π2py , Π2pz.

The two highest level orbitals are degenerate and are both singly occupied in the boron molecule as shown in the molecular orbital electron configuration above.

Note KK refers to the core electrons.

Answer 2

According to molecular orbital theory, atomic orbitals combine to form molecular orbital. Number of molecular orbitals are equal to number of atomic orbitals. Further, of the total number of molecular orbitals, half are called as bonding molecular orbital while remaining are anti-bonding molecular orbital. In case, if system contains lone pair of electrons, they occupy non-bonding molecular orbital. Highest occupied molecular energy levels are referred as HOMO, while lowest unoccupied molecular energy levels are referred as LUMO.

In case of B2 molecule, two B atoms combines to generate molecular orbitals. Attached is the MOT diagram of B2 molecule

From the attached figure, it is clearly evitable that high occupied energy level in B2 is π. Also, it must be noted both pi molecular orbitals i.e. Pi 2Px and Pi 2Py at highest energy level (occupied).