Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. It is determined by the number of bonds and lone pairs of electrons surrounding a central atom, which influences the shape of the molecule. Common geometries include linear, trigonal planar, tetrahedral, and octahedral, each defined by specific bond angles. Understanding molecular geometry is essential in chemistry because it affects the physical and chemical properties of substances. For example, the shape of a molecule can influence its reactivity, polarity, and interactions with other molecules, impacting processes such as biological functions and chemical reactions.