Table showing different types of hybridization and geometry of molecules
To account for the bonding in simple diatomic molecules like HF, we picture the direct overlap of ‘s’ and ‘p’ orbitals of isolated atoms.
But how can we account for the shapes of so many molecules and polyatomic ions through the overlap of spherical ‘s’ orbitals, dumbbell–shaped ‘p’ orbitals, and cloverleaf–shaped ‘d’ orbitals?
To explain such facts, Linus Pauling proposed that the valence atomic orbitals in the molecule are different from those in the isolated atoms. Indeed, quantum mechanical calculations show that if we “mix” specific combinations of orbitals mathematically, we obtain new atomic orbitals. The spatial orientations of these new orbitals lead to more stable bonds and are consistent with observed molecular shapes. The process of orbital mixing is called hybridization, and the new atomic orbitals are called hybrid orbitals. Two key points about the number and type of hybrid orbitals are that
- The number of hybrid orbitals obtained equals the number of atomic orbitals mixed.
- The type of hybrid orbitals obtained varies with the types of atomic orbitals mixed.
You can imagine hybridization as a process in which atomic orbitals mix, hybrid orbitals form and electrons enter them with spins parallel (Hund's rule) to create stable bonds. In truth, though, hybridization is a mathematically derived result from quantum mechanics that accounts for the molecular shapes we observe.
Hybridization of Orbitals:
Type of Hybrid Orbitals:
We postulate the presence of a certain type of hybrid orbital after we observe the molecular shape. As we discuss the five common
types of hybridization, notice that the spatial orientation of each type of hybrid orbital corresponds with one of the five common
electron–group arrangements predicted by VSEPR theory.
In larger molecules, the geometry changes. This is because of the orientation of orbitals of different energy. In order to minimize the orientation, the paired electrons with less energy get shifted to orbitals of different energy thereby, the valence shells come to a same energy level due to unpaired electrons present in each shell. Therefore, a hybrid orbital may be defined as a set of orbitals with identical properties formed from the combination of two or more orbitals with different energies.
Different types of hybridization are sp hybridization, sp2 Hybridization, sp3 hybridization, sp3d hybridization, sp3d2 hybridization.