Determine the Lewis structures of the following compounds, and determine which have dipole moments (i.e. which ones are polar?). Choose yes or no. Does CH have a dipole moment? Does CHCl have a dipole moment? Does CH2 have a dipole moment? Does CH3 have a dipole moment? Does CCl have a dipole moment?
The Correct Answer and Explanation is:
Answers:
- Does CH have a dipole moment? → Yes
- Does CHCl have a dipole moment? → Yes
- Does CH₂ have a dipole moment? → Yes
- Does CH₃ have a dipole moment? → No
- Does CCl have a dipole moment? → Yes
Explanation:
To determine if a molecule has a dipole moment, we must consider two factors: the electronegativity differences between atoms and the molecular geometry. A dipole moment arises when there is an uneven distribution of electron density, creating a partial positive and partial negative side in a molecule.
- CH (methylidyne radical) consists of one carbon atom and one hydrogen atom. Since carbon is more electronegative than hydrogen, a dipole forms with electrons pulled slightly toward carbon. Therefore, CH is polar and has a dipole moment.
- CHCl contains a carbon atom bonded to hydrogen and chlorine. Chlorine is significantly more electronegative than both carbon and hydrogen, pulling electron density toward itself. The molecular shape does not cancel out this effect, so CHCl has a dipole moment and is polar.
- CH₂ typically refers to a methylene group. In its simplest form (a neutral CH₂), the geometry is bent due to the presence of a lone pair on carbon. This asymmetry and the differing electronegativity between carbon and hydrogen lead to a net dipole moment. Thus, CH₂ is polar.
- CH₃ (methyl radical) has a trigonal planar or slightly pyramidal shape, depending on whether it’s neutral or an ion. The three C–H bonds are identical and symmetrically arranged. Their dipoles cancel each other out, making the molecule nonpolar, so CH₃ has no dipole moment.
- CCl involves a carbon and a chlorine atom. Chlorine is more electronegative than carbon, drawing electrons toward itself and creating a dipole. Since it’s a diatomic molecule, there’s no symmetry to cancel the dipole, so CCl is polar and has a dipole moment.
In summary, all molecules listed except CH₃ exhibit polarity and possess dipole moments.
