Which Molecule Does Not Have A Dipole Moment

February 18, 2024

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Concept:

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Dipole moment:

The polarity or ionic character of a covalent bond is considered in terms of its dipole moment.
The dipole moment of a bond (µ) of a bond is defined as the product of the magnitude of charge (q) at one pole and the distance (r) between the centres of positive and negative charges.

µ = q × r

1 D = 3.33564×10-19 cm

For a homonuclear diatomic molecule, H2, Cl2, etc., the bond is non-polar and the dipole moment is zero.
For heteronuclear molecules like HF, HCl, etc., the dipole moment is non-zero and equal to the bond dipole moment.

The dipole moment of Triatomic and Polyatomic molecules:

For triatomic and polyatomic molecules, the dipole moment is obtained by the vectorial addition of individual bond moments.
i.e., their resultant dipole moment depends upon the geometry of the molecule.

Explanation:

1. SO3

SO3 has a trigonal planar structure.
In it, the individual S-O bond moments cancel out each other so that the net dipole moment is zero.
i.e., µ = 0 for SO3.

2. SO2

It has a bent structure due to the presence of one lone pair.
Is a polar molecule.
In it, the individual S-O bond moments do not cancel out each other so that the net dipole moment is not zero.
It has a permanent dipole moment.

3. H2S

It has a bent structure due to the presence of one lone pair.
Is a polar molecule.
In it, the individual H-S bond moments do not cancel out each other so that the net dipole moment is not zero.
It has a permanent dipole moment.

4. CS2

CS2 is one of the molecules which does not possess a dipole moment.
It is a linear molecule and therefore it does not have a permanent dipole moment.

Hence, CS2 and SO3 are molecules that do not have a permanent dipole moment.

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