CHEMISTRY COMMUNITY

So I understand that antibonding is when two atomic orbitals are out of phase, but what does that really mean - and can someone also explain the meaning of it in the MO diagram?

If a molecular orbital is antibonding, it means there is a nodal plane between the two nuclei and the energy of the orbital is higher than the atomic orbitals to which it correlates. Therefore, electrons in an antibonding molecular orbital are less stable than they would be if the atoms were separated or not bonding to each other. These electrons are less likely to be found between the nuclei, which we typically call the "bonding region." Therefore electrons in antibonding orbitals destabilize the bond.