Knowledge of the shapes of molecules is particularly important in molecular biology, where the shape of a molecule can determine its function. The shapes of large biomolecules can often be predicted by first studying patterns in simple molecules, such as methanal (formaldehyde, H₂C=O), which was once used in preservatives for biological samples. Predict the shape of a methanal molecule.

ANTICIPATE Carbon atoms typically form four bonds. The central C atom in methanal has four bonds, so you should not expect there to be any lone pairs of electrons on the central atom.

PLAN Write the Lewis structure and identify the electron arrangement around the central atom (the C atom, in this case). Treat each multiple bond as a single unit. Then identify the overall shape of the molecule.