9 posts • Page 1 of 1
Yes, you would likely have to draw/imagine the shape of a molecule and consider the dipole moments within it. For example, CH4 is symmetrical, so the dipole moments between C-H bonds cancel. However, H2O is not, and this can be seen by the strong dipoles in H-O bonds.
If the molecule consists of two atoms and the electronegativity of one atom is significantly higher than the other, the molecule can be considered polar. For molecules with 3 or more atoms, drawing the structure and then writing the dipole arrows will allow you to assess if the molecule is polar.
In order to determine whether a molecule is polar or non-polar, you would have to draw out the lewis structure first. Then you would identify the bonds and lone pairs around the central atom. If the molecule has symmetry around the central atom, the dipoles cancel out and the molecule is non-polar. If the molecule is asymmetric, then it is polar.
Generally, if there is a particular part of the molecule that is more electronegative and the shape of the molecule does not allow for the charges to cancel (e.g. if the structure is not symmetrical), then the molecule is polar.
The greater difference in the electronegativity between two atoms, the more polar the bond between them will be because the more electronegative atom will have a greater pull on the electrons, and that side of the bond will be more negative.
Polar bonds occur when two atoms of substantially different electronegativities bond with each other. For the purposes of this class, I believe we can generally label hydrogen and carbon as having low electronegativity while nitrogen, oxygen, and fluorine have high electronegativity. I mention these atoms because of how common they are in molecules. If there is a bond between one of the atoms with low electronegativity and one of the atoms with high electronegativity, the bond will be polar with slightly charged dipoles. Sometimes, dipoles in a molecule cancel out which makes drawing molecules useful (though not necessary) for determining if a molecule is polar.
Who is online
Users browsing this forum: No registered users and 1 guest