When the 1s wave functions of the two HH atoms are linearly combined, we get a sigma (s) bonding orbital, denoted as s1s in the diagram here. This approach is called linear combination of atomic orbitals (LCAO), inthe MO approach. In this approach, the sum of the two 1s orbitals (one for each atom) is the bonding orbital. In terms of wave mechanics, the two waves constructively interact. The difference of the two orbitals forms the antibonding orbital, s1s*, due to destructive interference. It is interesting to note that the anti bonding orbital is at a higher energy than the 1s atomic orbital. The energy level can be represented below:
Each orbital accommodates two electrons, and the two electrons in H−HH−H fill the s1s molecular orbital (MO). Obviously, as a result of the formation of the H2H2molecule, the energy of the system is lowered and becomes more stable.
The quantum mechanics of the chemical bonding is a little complicated, but the logic and concept are as simple as described above. I have written a program for the DOS version of CAcT to plot electron densities of the s1s and s1s* electron densities, but the program cannot be executed on the web page. The execution of these types of simulations is sometimes shown during the lecture.
Answers & Comments
When the 1s wave functions of the two HH atoms are linearly combined, we get a sigma (s) bonding orbital, denoted as s1s in the diagram here. This approach is called linear combination of atomic orbitals (LCAO), inthe MO approach. In this approach, the sum of the two 1s orbitals (one for each atom) is the bonding orbital. In terms of wave mechanics, the two waves constructively interact. The difference of the two orbitals forms the antibonding orbital, s1s*, due to destructive interference. It is interesting to note that the anti bonding orbital is at a higher energy than the 1s atomic orbital. The energy level can be represented below:
Each orbital accommodates two electrons, and the two electrons in H−HH−H fill the s1s molecular orbital (MO). Obviously, as a result of the formation of the H2H2molecule, the energy of the system is lowered and becomes more stable.
The quantum mechanics of the chemical bonding is a little complicated, but the logic and concept are as simple as described above. I have written a program for the DOS version of CAcT to plot electron densities of the s1s and s1s* electron densities, but the program cannot be executed on the web page. The execution of these types of simulations is sometimes shown during the lecture.