Two dichloroethylene molecules with the same chemical formula 1C2H2Cl22, but different arrangements of atoms are shown. (b) Which form of dichloroethylene has a dipole moment of 2.39 D, and which has a dipole moment of 0.00 D?

Key Concepts

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. The shape of a molecule influences its polarity, as the spatial distribution of polar bonds can lead to an overall dipole moment. For dichloroethylene, the arrangement of chlorine and hydrogen atoms affects whether the molecule is symmetrical or asymmetrical, which is crucial for determining its dipole moment.

Polarity and Dipole Moment

Polarity in molecules arises from differences in electronegativity between atoms, leading to uneven distribution of electron density. A dipole moment is a vector quantity that measures the separation of positive and negative charges in a molecule. Molecules with a net dipole moment, such as one form of dichloroethylene, exhibit polarity, while symmetrical molecules may have a dipole moment of zero due to cancellation of individual bond dipoles.

Isomerism

Isomerism occurs when two or more compounds have the same molecular formula but different structural arrangements of atoms. In the case of dichloroethylene, the two isomers can have different physical properties, including dipole moments. Understanding isomerism is essential for predicting how the arrangement of atoms affects molecular behavior, such as polarity and reactivity.