Chemical Bonding and Structure - Hybridization (HL only)

Hybridization is the conceptual process of mixing atomic orbitals (such as $s$ and $p$ orbitals) to form new hybrid orbitals that are degenerate (equal in energy) and suitable for the pairing of electrons to form chemical bonds.

$sp^3$ Hybridization: Formed by mixing one $2s$ and three $2p$ orbitals. This results in four $sp^3$ hybrid orbitals arranged in a tetrahedral geometry with bond angles of approximately $109.5^\circ$ (e.g., in $CH_4$ or $NH_3$).

$sp^2$ Hybridization: Formed by mixing one $2s$ and two $2p$ orbitals. This results in three $sp^2$ hybrid orbitals arranged in a trigonal planar geometry with bond angles of $120^\circ$. One unhybridized $p$ orbital remains perpendicular to the plane (e.g., in $C_2H_4$ or $BF_3$).

$sp$ Hybridization: Formed by mixing one $2s$ and one $2p$ orbital. This results in two $sp$ hybrid orbitals arranged in a linear geometry with bond angles of $180^\circ$. Two unhybridized $p$ orbitals remain (e.g., in $C_2H_2$ or $CO_2$).

Sigma ($\sigma$) bonds: These are formed by the head-on overlap of atomic or hybrid orbitals along the internuclear axis. All single covalent bonds are $\sigma$ bonds.

Pi ($\pi$) bonds: These are formed by the sideways overlap of unhybridized $p$ orbitals. A double bond consists of one $\sigma$ and one $\pi$ bond; a triple bond consists of one $\sigma$ and two $\pi$ bonds.

The hybridization of an atom can be predicted by the number of electron domains: $2$ domains $\rightarrow sp$, $3$ domains $\rightarrow sp^2$, $4$ domains $\rightarrow sp^3$.