Final answer:
Isomers have the same molecular formula but different structures, such as the structural isomers ethanol and dimethyl ether. Lewis structures indicate that both molecules have a trigonal planar electron geometry around the oxygen atom, with bent molecular geometries.
Step-by-step explanation:
Isomers are compounds with the same molecular formula but different arrangements of atoms, and they can be structural or geometric isomers. The structural isomers of alkanes and alkenes differ in how the atoms are covalently bonded together. Ethanol (C₂H₅OH) and dimethyl ether (CH₃OCH₃) serve as an example, both having the formula C₂H₆O but differing in structure. In ethanol, the oxygen is bonded to a hydrogen atom and an ethyl group (CH₃CH₂-), while in dimethyl ether, oxygen is bonded to two methyl groups (CH₃-).
The Lewis structures of these compounds help visualize their molecular geometries. For ethanol, this shows a bent geometry around the oxygen atom due to the two lone electron pairs, resulting in a trigonal planar electron geometry and a bent molecular geometry. Conversely, dimethyl ether, which also has two lone pairs on the oxygen, presents a similar electron geometry but differs in molecular geometry due to the presence of two methyl groups instead of one ethyl group and a hydrogen atom.
It is important to recognize that isomers have distinct physical and chemical properties despite having the same molecular formula, which is fundamentally relevant to the study and application of organic chemistry.