Animation of the structure of a molecule of ammonia (NH3). This molecule has a trigonal pyramidal geometry, with three hydrogen atoms (white) forming a triangular base below a capping nitrogen atom (dark blue). This geometry is adopted as the hydrogen atoms repel each other, but the nitrogen atom also contains a lone pair of electrons, which repels the hydrogens as well. See clip K004 3561 for the molecule showing the lone pair, and K004 3568 for the molecule showing the angle between the atoms.