This video lecture from Fundamental Principles of Organic Chemistry (F.Sc. second year Chemistry) covers sp mode of hybridization and the formation of two pi bonds by the un-hybridized orbitals perpendicular to each other. Alkynes show sp hybridization where one s and a p orbital hybridizes to form two degenerate sp orbitals in a linear geometry. Two pi bonds with perpendicular overlapping are formed as a result. A summary of all hybridization types and corresponding geometries is presented at the end.