We have reviewed the concepts of energy and position for electrons in isolated Hydrogen atoms. However, atoms seldom exist in isolation. Let’s study the bonding of Hydrogen atoms.
Let’s consider the two lowest energy levels for an electron in a Hydrogen atom.
The electron is going to be mostly in the lowest energy level.
For two atoms that are far from each other and do not interact, the orbitals and energy levels for electrons in each atom are going to stay the same.
However, when we consider two atoms together, each energy state splits into two energy states called bonding and anti-bonding states.
See how energy splitting changes as you vary the separation between the two atoms.
For an electron in a bonding state, the wavefunctions of the two orbitals interfere constructively in the middle. That means if you conduct many experiments to find the electron, in many cases you will find the electron between the two atoms.
This is the bonding state between the two 1s orbitals.
For an electron in an antibonding state, the wavefunctions of the two orbitals interfere destructively in the middle. That means if you conduct many experiments to find the electron, in many cases you will rarely find the electron between the two atoms.
In a Hydrogen molecule, both electrons can be in the 1s bonding state whose energy decreases as the two atoms become closer. What about the total energy?
The attractions and repulsions between the charges also contribute to the total Energy.