What is the molecular dipole?
Permanent dipoles. These occur when two atoms in a molecule have substantially different electronegativity: One atom attracts electrons more than another, becoming more negative, while the other atom becomes more positive. A molecule with a permanent dipole moment is called a polar molecule.
Zero dipole moment is the dipole moment between two atoms being zero. It depends on the polarities of individual bonds and the geometry of the atoms. For example CO2 , two opposing oxygen atom with carbon in the center as it's geometry . So, it has zero dipole moment.
- In physics, the electric dipole moment is a measure of the separation of positive and negative electrical charges within a system, that is, a measure of the system's overall polarity. The electric field strength of the dipole is proportional to the magnitude of dipole moment.
- So,in addition to bond polarity and structure, the unshared pair of electrons also influence dipole moment values. The dipole moment of NF3 is expected to be larger than NH3. But the actual value of D.M of NF3 is 0.23D while that of NH3 is 1.46D ( where D is Debye).
- The Nitrogen atom is more electronegative and therefore the valence electrons are near them more often. This makes it more negative. The Hydrogen atoms at the bottom of the structure are then more positive. Therefore, H2O is a polar molecule.
Such molecules are said to be polar because they possess a permanent dipole moment. A good example is the dipole moment of the water molecule. Molecules with mirror symmetry like oxygen, nitrogen, carbon dioxide, and carbon tetrachloride have no permanent dipole moments.
- Carbon tetrachloride,CCl4, has a net dipole moment of zero. Even though each of the four C-Cl bond is distinctly polar, the resultant moment of any three of them is equal in magnitude but opposite in direction to the moment due to the fourth one. So, the molecule's net dipole moment is zero, and it is non-polar.
- - A molecule with two strong bond dipoles can have no molecular dipole if the bond dipoles cancel each other out by pointing in exactly opposite directions. For example, in carbon dioxide (linear molecule) carbon-oxygen bonds have a large dipole moment.
- Dipole-Dipole interactions result when two dipolar molecules interact with each other through space. When this occurs, the partially negative portion of one of the polar molecules is attracted to the partially positive portion of the second polar molecule.
This is because the charge is equally distributed amongst the entire molecule. When molecules have an even charge distribution and no dipole moment, then they are nonpolar molecules. CO2 is a linear molecule, so our dipoles are symmetrical; the dipoles are equal in magnitude but point in opposite directions.
- The BF3 molecule has a symmetrical trigonal planar geometry, like the SO3 molecule. In such a structure, the resultant moment of any two B-F dipoles is equal in magnitude but opposite in direction to the moment of the third one. So, the net dipole moment of the BF3 molecule is zero, and it is non-polar.
- CO has two C-O bonds. The dipoles point in opposite directions, so they cancel each other out. Thus, although CO2 has polar bonds, it is a nonpolar molecule. Therefore, the only intermolecular forces are London dispersion forces.
- D) The SO2 molecule has a dipole moment, whereas the CO2 molecule has no dipole moment. Include Lewis structures in your explanation. In CO2 the molecule is linear and the opposing C-O bonds provide no net dipole moment. While in SO2 the lone pair of electrons on S create a bent structure with a net dipole moment.
Updated: 16th October 2019