So, according to this diagram, we see that the y axis is energy. And so the lower we go, the less energy we have. The higher we go, the more energy we have. Now, once again, according to Quantum Mechanics, if we begin with two atomic orbitals, we have to form two molecular orbitals. So far we've only seen one. Well, the second one is shown right up here, and it's called the phi antibonding molecular orbital.