Determining bond angles in molecules requires more than just knowing the molecular formula; structural isomers play a crucial role. For instance, C3H6 can represent both propene and cyclopropane, each with distinct bond angles due to their different structures. VSEPR theory is essential for predicting these angles, as it accounts for electron pair repulsion, including the influence of lone pairs. Additionally, computational simulations can provide precise bond angles, while approximate rules exist for estimating angles based on atom combinations. The discussion also highlights the complexity of molecular geometry, including exceptions like Drago's rule, emphasizing that a thorough understanding of molecular structure is necessary for accurate bond angle determination.