Final answer:
A molecule with three single bond pairs and one unshared pair around a central atom has a trigonal pyramidal shape due to the geometry created by the electron groups, including the influence of the lone pair.
Step-by-step explanation:
A molecule that has a central atom surrounded by three single bond pairs and one unshared pair would have a trigonal pyramidal shape. This is because the molecule has four electron groups around the central atom, with three of these groups being bonding pairs and one being a lone pair, resulting in a molecular geometry that resembles a tetrahedron missing a vertex. The presence of the lone pair influences the molecular geometry, causing the bond angles to be slightly less than the ideal angle of 109.5° due o lone pair-bond pair (LP-BP) repulsions.