Question

The molecule with non-zero dipole moment?
(a)- $BC{{l}_{3}}$
(b)- $BeC{{l}_{2}}$
(c)- $CC{{l}_{4}}$
(d)- $NC{{l}_{3}}$

Answer 1

Hint: The dipole moment is the product of negative or positive charge and the distance between the centers of positive and negative charges. The dipole moment is directed towards the more electronegative atom in the compound. The opposite direction of the dipole moment in the molecule cancels each other.

Complete step by step answer:
The dipole moment is the product of the positive or negative charge and the distance between centers of the positive and negative charges. It is denoted by$\mu $. It is denoted by the arrow with its tail at the positive center and head pointing towards the negative end:
$(+\mapsto -)$
The dipole moment is directed towards the more electronegative atom.
Let us see all the options:
(a)- $BC{{l}_{3}}$
The structure of $BC{{l}_{3}}$is:

The chlorine atom is more electronegative than the boron atom hence, the dipole moment will direct towards the chlorine atom. Since the dipole moment of one chlorine atom is canceled by the resultant dipole moment of the other 2 chlorine atoms. Hence, it has zero dipole moment.
(b)- $BeC{{l}_{2}}$
The structure of $BeC{{l}_{2}}$is:

The chlorine atom is more electronegative than the beryllium atom hence, the dipole moment will direct towards the chlorine atom. Both the dipole moments of the chlorine atom are in the opposite direction and hence cancel out. So, the dipole moment is zero.
(c)- $CC{{l}_{4}}$
The structure of $CC{{l}_{4}}$is:

The chlorine atom is more electronegative than the carbon atom hence, the dipole moment will direct towards the chlorine atom. It is a symmetrical molecule, and the molecular dipole moment is found to be zero.
(d)- $NC{{l}_{3}}$
The structure of $NC{{l}_{3}}$is:

The chlorine atom is more electronegative than the nitrogen atom hence, the dipole moment will direct towards the chlorine atom. Since the $NC{{l}_{3}}$has a pyramidal structure due to the presence of a lone pair, there is a net resultant dipole moment.

Hence, the correct answer is an option (d)- $NC{{l}_{3}}$


Note: The determination of the dipole moment helps find the polarity of the molecule. The higher the dipole moment of the molecule, the higher is the polarity of the molecule. It can also be used in calculating the ionic character.