Hybridization

Learning Objective LO 2.21 The student is able to use Lewis diagrams and VSEPR to predict the geometry of molecules, identify hybridization, and make predictions about polarity.

Basics of Covalent Bonding The simplest way to describe covalent bonding is valence bond theory. Valence bond theory simply describes covalent bonding as the result of the overlap of half-filled valence-level atomic orbitals. The overlapping orbitals create a new region between the atoms where the pair of atoms are shared.

Bonding Orbitals Valence bond theory does well to explain the bonding in molecules that have just two atoms.

Bonding Orbitals Data (such as bond length and bond angles) suggest that covalent bonding doesn’t include only the traditional atomic orbitals (s, p, d, f). For example, a simple explanation for the formation of a water molecule would involve the two half-filled p-orbitals in oxygen overlapping with s orbitals from two different hydrogen atoms. Since p-orbitals are oriented 90° from each other, a water molecule would seem to have an angle of 90° between its covalent bonds. The actual bond angle is larger than this, suggesting further explanation is required.

Hybridization For molecules with more than two atoms, the orbitals around the central atom appear to be more like hybrids of the traditional atomic orbitals. These hybrid orbitals are identical, both in terms of shape and energy. This explains why the valence electrons often spread out more than predicted by an atomic orbital diagram.

sp3 hybridization

sp2 hybridization

sp hybridization

sp3d hybridization

sp3d2 hybridization

Determining the type of Hybridization STEP 1 – Identify the number of “electron domains”, or locations that have electron pairs, around the central atom. A single “electron domain” includes… * a single bond * a double bond * a triple bond * one unbonded electron pair

STEP 2 – Each electron domain requires a hybrid orbital. For each hybrid orbital that is required, an atomic orbital had to be hybridized. Simply translate your count of electron domains to the type of hybridization that involves that many atomic orbitals.

# of domains Hybridization 2 sp 3 sp2 4 sp3 5 sp3d 6 sp3d2