Electric dipole moment in gaseous species.

[V0ODO0CH1LD]

Homework Statement

Consider the following species in the gaseous state: $NF_3, \ BeF_2, \ BCl_3, \ KrF_4 \ and \ SeO^{2-}_4$.
Which of them have electric dipole moment?

Homework Equations

The Attempt at a Solution

I tried google, but I can't figure out how to check that..

 

[AGNuke]

Can you draw their representative structures, like you draw tetrahedral structure for methane? That can give you the clue.

 

[V0ODO0CH1LD]

How is drawing the representative structures supposed to give me a clue on which species have electric dipole moment? Is it like, in the case with $BeF_2$, where $Be$ is left with a positive charge of 2+ and each $F$ with a negative charge of 1-. So it will have electric dipole moment?

 

[AGNuke]

Example to what I said:

BeF₂ in gaseous form is a linear molecule, like F---Be---F, so the dipoles are F---Be and Be---F. Now can you determine the net dipole moment?

What I asked you is to draw the structures of molecules using VBT and VSEPR theory. Like in the case of NF₃

 

[DeeNos]

I would approach this question by first understanding the concept of electric dipole moment. An electric dipole moment is a measure of the separation of positive and negative charges within a molecule, and it is a vector quantity. This means that it has both magnitude and direction.

To determine which of the given species have electric dipole moments, we need to consider the molecular geometry and the distribution of charges within each molecule. NF3, BeF2, BCl3, and KrF4 are all symmetrical molecules, meaning that their molecular geometries have a high degree of symmetry. This symmetry results in a cancellation of the dipole moments, and therefore, these molecules do not have an electric dipole moment.

On the other hand, SeO42- is a non-symmetrical molecule, and it has a bent molecular geometry. This results in an unequal distribution of charges within the molecule, and it has a non-zero electric dipole moment.

In summary, out of the given species, only SeO42- has an electric dipole moment. This is because its molecular geometry is non-symmetrical, leading to an unequal distribution of charges within the molecule.