Molecular Orbital Theory of Homonuclear Diatomic Molecules

While the specific shapes of molecular orbitals (their reliance on r and z in a cylindrical coordinate system) varies for each molecule, the symmetry of the system totally determines their dependency on the angle f as expressed by the quantum number l and their g or u behaviour when inverted. For homonuclear diatomic molecules, these features apply to all molecular orbitals. Furthermore, for nearly all homonuclear diatomic compounds, the relative ordering of orbital energies is the same. As a result, we may draw a molecular orbital energy level diagram similar to the one used to produce the electronic configurations of atoms in the periodic table. The molecular orbital energy level diagram is just as important for understanding diatomic molecules’ electrical structure as the atomic orbital diagram is for comprehending atoms.

Treated as moving under the influence of the atomic nuclei in the whole molecule

Molecular orbital theory is a method for identifying molecular structure in which electrons are viewed as moving under the influence of the nuclei in the whole molecule rather than being attributed to particular bonds between atoms. Quantum physics binds the spatial and energetic properties of electrons within atoms to form orbitals that contain them. While atomic orbitals have electrons assigned to a single atom, molecular orbitals, which encircle a molecule’s atoms, contain valence electrons between them. Resonance and molecular-orbital methods are two popular quantum mechanics-based ways to formulate the structures and characteristics of organic molecules. There has previously been much debate over which of these methodologies is truly more useful for qualitative goals, and adherents to either one could hardly bear the notion that their choice was flawed. In reality, neither is unquestionably superior, and one should be familiar with and employ both; they are more complementary than competitive.

Electrons in a molecule are not assigned to individual chemical bonds between atoms

Molecular orbital concept (MO theory or MOT) is a way of employing quantum mechanics to describe the overall electronic structure of the molecule in chemistry. Early in the twentieth century, it was proposed.

Electrons in a molecule are not ascribed to distinct chemical interactions between atoms in molecular orbital theory, but are instead viewed as moving under the effect of the atomic nuclei across the molecule. As molecular orbitals that surround two or even more atoms in a molecule and include valence electrons between atoms, quantum mechanics describes the spatial or kinetic properties of electrons.

The core ideas of quantum physics are molecular orbital and valence bond theory.

Molecular orbital theory electronic configuration

It is impossible to forecast the relative energies of 3σg and 1πu. Calculations reveal that the energy of 1πu is less than 3σg for all elements up to Nitrogen (Z=7), but this tendency reverses after that. When the electrons in the oxygen molecular orbitals are filled, the lowest energy state corresponds to two electrons in the 1πu orbitals, indicating that the oxygen molecule is paramagnetic. The bond order, which is given by, is the other amount of interest.

bond order = 1/2 (nbonding − nantibonding)

where bonding is the number of electrons in the bonding Molecular orbitals, and antibonding is the number of electrons in the bonding Molecular orbitals, and vice versa. The bond order is a metric that indicates how strong a bond is.

Conclusion

If the electron configuration of the parent atoms is known, a few basic rules may be used to generate Molecular orbital energy-level diagrams for diatomic compounds. The number of molecular orbitals in a molecule is equal to the number of interacting atomic orbitals. The overlap of the parent orbitals determines the difference between bonding and antibonding molecular orbital combinations, which reduces as the energy difference between the parent atomic orbitals grows. The electrical structures of nearly all homonuclear diatomic molecules (molecules with two identical atoms) may be described using this method. The O₂ molecule has two unpaired electrons, as predicted by the molecular orbital method, and hence is attracted to a magnetic field. Most compounds, on the other hand, only have pairs of electrons. A molecular orbital energy-level diagram that is skewed or slanted toward the more electronegative element can be used to perform a similar approach on molecules having two different atoms, known as heteronuclear diatomic molecules. Molecular orbital theory may describe and even predict the chemistry of molecules having an odd number of electrons, such as NO.