13.3.2—Shape of, and bond angles in, molecules

An sp-hybridised atom has two electron domains and a linear arrangement near 180°. sp² gives three domains and a trigonal-planar arrangement near 120°, while sp³ gives four domains and a tetrahedral arrangement near 109.5°.

These are idealised local geometries. Lone pairs and substituents can distort angles, and the hybridisation label refers to the atom’s bonding environment rather than the whole molecule’s shape.

The carbon atoms in ethyne are sp and linear; each alkene carbon in ethene is sp² and trigonal planar; methane carbon is sp³ and tetrahedral.

Do not call every molecule with one sp³ atom tetrahedral overall. Apply the geometry around the specific atom being considered.