sp2hybridisering

Sp2 hybridization is a concept from valence bond theory describing how certain atoms form bonds in a trigonal planar arrangement. It results from mixing one s orbital with two p orbitals to produce three new equivalent orbitals, called sp2 hybrids. These hybrids point toward the corners of a triangle and are arranged about 120 degrees apart. The remaining unhybridized p orbital on the atom remains perpendicular to the plane and can participate in pi bonding.

In this model, the central atom uses its sp2 hybrids to form sigma bonds with surrounding atoms (or lone pairs), giving three regions of electron density. If all three regions are bonds, the geometry is planar with bond angles near 120 degrees. The unhybridized p orbital overlaps with a p orbital on a neighboring atom to form a pi bond, which is responsible for multiple bonds such as C=C in alkenes.

Common examples include ethene (C2H4), where each carbon is sp2-hybridized and participates in one sigma bond to the other carbon, two sigma bonds to hydrogens, and a pi bond formed from unhybridized p orbitals. Carbonyl compounds like formaldehyde (CH2O) and boron trifluoride (BF3) also feature sp2-hybridized centers.

Limitations of sp2 theory arise because real molecules are better described by molecular orbital theory, especially for delocalized systems and resonance. Nevertheless, sp2 provides a simple and useful picture for understanding the geometry and reactivity of many organic and inorganic species with three electron-density regions around the central atom.