Final answer:
The bond order decreases by 0.5 for B2, C2, and F2 when one electron is added to the neutral molecule. The bond order remains unchanged for P2.
Step-by-step explanation:
The bond order of a molecule is a measure of the stability of the bond. When you add an electron to a neutral molecule, the bond order can either increase or decrease depending on the molecular orbital diagram. In this case, we need to determine how the bond order changes for B2, C2, P2, and F2 when an electron is added.
According to the molecular orbital diagrams, B2 and C2 have a bond order of 2, P2 has a bond order of 1, and F2 has a bond order of 1. When you add an electron to these molecules, the bond order will decrease by 0.5, except for P2 which remains unchanged. Therefore, the bond orders after adding an electron would be B2 - 1.5, C2 - 1.5, P2 - 1, and F2 - 0.5.