Final answer:
With four bonded atoms and no lone pairs, the molecular shape is tetrahedral, like methane (CH4). Presence of lone pairs can lead to other shapes like seesaw or square pyramidal based on trigonal bipyramidal electron-group geometry.
Step-by-step explanation:
When four atoms are bonded to a central atom, several different molecular shapes are possible, depending on the number of lone pairs on the central atom. However, with no lone pairs and only bonded atoms, the shape that the molecule takes is tetrahedral. This is due to the electron-pair geometry which orients the four groups in the direction of a tetrahedron. An example of a molecule with a tetrahedral shape is methane (CH4).
If lone pairs are present, the shape may differ. For instance, a molecule with four single bonds and a lone pair would have a trigonal bipyramidal electron-group geometry and could potentially have shapes such as seesaw or square pyramidal. Octahedral geometry occurs in molecules with six regions of electron density.