Final answer:
When two atomic orbitals combine in phase, they form a bonding orbital which is lower in energy. Removing an electron from this orbital will decrease bond order. The resulting molecular orbital will have sigma symmetry.
Step-by-step explanation:
When two atomic orbitals combine in phase, they form a bonding orbital which is lower in energy than the original atomic orbitals. On the other hand, when the atomic orbitals combine out of phase, they form an antibonding orbital which is higher in energy than the original orbitals. In this specific case, the molecular orbital that results from the in-phase combination will be a bonding orbital. Removing an electron from the resulting orbital will decrease the bond order, as it reduces the number of bonding electrons.
The molecular orbital that results from the in-phase combination will have sigma symmetry, which means it is symmetric about the internuclear axis. It is important to note that pi symmetry is not associated with a molecular orbital resulting from the in-phase combination of these two atomic orbitals.