1. If we remove an electron from a bonding orbital, the bond in the ion is weaker than that in the molecule.

2. So, let's start our discussion of a bonding orbital.

3. And so this lower level is called a bonding orbital, and it is a bonding molecular orbital.

4. It turns out that the antibonding orbital is a little bit higher from the atomic orbital level than the bonding orbital is lower.

5. And this again is what we're going to call a bonding orbital.

6. Now, from your book as well, this is the pz's of the two atomic orbitals forming the bonding orbital.