my teacher told me that polar bonds have a difference in elecronegativities of .4-2.1
is that the only way to find if a bond is polar?
also how would you find out if the MOLECULE is polar or not?
- i think i remember my teacher saying something about dipole moments...
To be polar, a molecule must have both of the following:
a. bonds that are polar AND
b. the molecule must NOT be symmetrical.
Electronegativity is the way to go to determine if a bond is polar.
The difference in electronegativities of atoms is indeed one way to determine if a bond is polar. A polar bond occurs when there is a significant difference in electronegativity between the two atoms involved in the bond. Typically, a difference in electronegativity greater than 0.4 indicates a polar bond, with values ranging from 0.4 to 2.1.
However, the presence of a polar bond does not necessarily make a molecule polar. To determine if a molecule is polar, you need to consider its molecular geometry and the overall distribution of its polar bonds.
One method to assess the polarity of a molecule is by examining its dipole moments. A dipole moment is a measure of the separation of positive and negative charges in a molecule. It occurs when a molecule has polar bonds that do not cancel each other out due to the molecule's shape or symmetry.
To determine if a molecule has a dipole moment, you can consider the following steps:
1. Identify polar bonds: Determine if the molecule contains polar bonds by comparing the electronegativities of the atoms involved in each bond.
2. Consider molecular geometry: Examine the shape of the molecule. If the molecule is linear or symmetrical (such as tetrahedral, trigonal planar, or octahedral), the polar bonds may cancel out, resulting in a nonpolar molecule. However, if the molecule is asymmetrical or bent, the dipole moment will not be canceled, making the molecule polar.
3. Analyze the vector sum of dipole moments: If you have determined that the molecule has polar bonds and an asymmetrical shape, calculate the vector sum of the dipole moments. If the vector sum is zero, the molecule is nonpolar. If it is nonzero, the molecule is polar.
Remember, a molecule can be polar even when its individual bonds are not polar if the geometry allows the polarities to add up or if it has lone pairs of electrons that affect its shape.