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Home > Articles > Electric Dipole Moment: Definitions, Formula, Significance, How to Calculate, and Unit
Updated on 04th April, 2023 , 8 min read
A dipole moment describes the existence of electric or magnetic charges in the vicinity of a system. The dipole moment is the mathematical product of the separation of these electric or magnetic charges. Since molecules with more than two polar connections are not symmetrical, they include dipole moments.
An electric dipole is defined as a pair of objects with equal and opposing charges that are separated by a limited distance.
For Example- Two charges of identical magnitude 'Q' separated by a distance "D." In this case, we suppose that the first charge is negative while the second charge remains positive. This specific combination is known as an electric dipole. As a result, we may say that an electric dipole is generated when equal and opposing charges are separated by an ensured distance.
The electric dipole moment formula for a pair of equal and opposing charges is
Dipole moments develop as a result of an electronegativity mismatch between two chemically linked atoms. A bond dipole moment quantifies the polarity of a chemical connection formed by two atoms in a molecule. It is based on the notion of the electric dipole moment, which is a measurement of the separation of negative and positive charges in a system. Because it has both magnitude and direction, the bond dipole moment is a vector quantity.
It is worth noting that the symbols + and - denote the two electric charges that occur in a molecule that are equal in magnitude but have opposing signs. They are separated by a fixed distance, often represented by a "d”.
The two forces acting on the dipole ends cancel each other out as free vectors, but they act as separate points. As a result, it produces a torque on the dipole. Also, the dipole has a rotational action as a result of the torque. The magnitude of the torque (t) when considering the dipole centre is the total of the two forces times their respective distance arms, which is-
|t| = 2q |E|a sin q
= |p||E| sin q
As a result, in the presence of a homogeneous electric field, a dipole tends to align itself parallel to the field in question. Other requirements must also be met for this to occur, such as orientation remaining at some non-zero angle designated as "q." Moreover, potential energy must be stored in the dipole at a preferred orientation ranging from q = 0 to q > 0.
A dipole moment is the product of the charge magnitude and the distance between the positive and negative charge centers.
Mathematically,
It is measured in Debye units, which are indicated by the letter "D”.
In a chemical bond between two atoms with differing electronegativities, the bond dipole moment may be represented as follows-
Where the bond dipole moment is,
The magnitude of the δ⁺ and δ⁻ partial charges,
where d represents the distance between δ⁺and δ⁻.
The bond dipole moment (μ) is a vector variable that runs parallel to the bond axis. The arrows used to indicate dipole moments in chemistry start at the positive charge and stop at the negative charge. When two atoms with different electronegativities interact, the electrons tend to migrate from their original locations towards the more electronegative atom. The bond dipole moment can depict this electron movement.
The following are some of the steps to calculate the electric dipole moment-
The charge in the CGS system is given in esu, and the bond length is in cm. As a result, the dipole moment is measured in esu cm. The charge is in the order of 1010 esu, while the separation is in the order of 108 cm. As a result, the order is 1018 esu cm. This magnitude is known as 1. As a result,
The charge in the SI system is represented in coulombs and thelength in meters. As a result, the coulomb meter is the SI unit of dipole moment.
In chemistry, the dipole moment indicated the polar nature or polarity of the molecules. The dipole moment of molecules is defined as the product of charge and the distance between atoms in a chemical bond. If the bond distance l separates +q amount of positive charge from q amount of negative charge, then dipole moment of polar molecule = q l.
The following are some of the dipole moments of chemistry-
The dipole moment of the HCl molecule is the same as the dipole moment of the HCl bond, which is 1.03D in the diatomic molecule of HCl.
The dipole moment of a beryllium fluoride molecule is zero. BeF₂has a straight shape. Each bond's dipole moments cancel each other out, resulting in a net dipole moment of zero. This is because the bond dipole moments in the BeF2 molecule are equal in magnitude and opposite in direction.
The dipole moment of thetriatomic CO₂(carbon dioxide) molecule is zero. Because of the molecule's linear form, the dipole moment of the C=O bond (2.3D) on one side cancels out the dipole moment on the opposite side, resulting in a net zero dipole.
The dipole moment of a triatomic H₂O water molecule is 1.84D. The dipole moment is not zero due to the bent shape of the water molecule. This is due to the consequent dipole moments of two O-H bonds tilted at 104.5 degrees with two oxygen atom lone pairs.
The dipole moment of tetra-atomic boron trihydride (BH3) is zero, whereas that of ammonia (NH3) is 1.49D. This is because BH3has a symmetrical structure and the three B-H bonds are at a 120-degree angle to each other. Because the three bonds are on a single plane, their dipole moments cancel each other out, resulting in a net dipole moment of zero. NH3, on the other hand, has a pyramidal structure with three N-H bonds and a single pair on the nitrogen atom. This results in a dipole moment of 1.49 D.
Moreover, while both NH3and NF3molecules have three N-H bonds and a lone pair on nitrogen atoms, the resultant dipole moment of NF3is smaller than that of NH3. This is due to the fact that the dipole produced between the lone pair and the nitrogen atom varies in NH3and NF3molecules. Since fluorine is more electronegative than nitrogen, it will draw all of the shared electrons from nitrogen in the opposite direction from the net dipole moment. As a result, the dipole moment of NF3diminishes. While nitrogen is more electronegative than hydrogen, it will draw all of the shared electrons from hydrogen in the same direction due to N-H bonding. As a result, the NH3dipole moment rises.
The dipole moments of the CH₄(methane) and CCl₄(carbon tetrachloride) molecules are zero. These two molecules, CH₄and CCl₄, have a symmetrical tetrahedral configuration. As a consequence, dipole moments of C-H bonds in CH₄cancel out and result in zero dipole moments, and dipole moments of C-Cl bonds in CCl₄molecules cancel out and result in zero dipole moments.
Even though the CH3Cl (methyl chloride) molecule has a tetrahedral shape, its dipole moment is not zero. This is due to the fact that methyl chloride's structure is not symmetrical and the dipole moments of the bonds C-Cl and C-H are not equal. As a result, the corresponding dipole moment is 1.86 D.
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By - Nikita Parmar 2024-09-06 10:59:22 , 6 min readAns. A dipole moment occurs when the electronegativity of two atoms participating in a bond differs. The greater the difference in electronegativity between the two atoms, the greater the dipole moment and polarity of the bond.
Ans. Carbon dioxide has a linear geometry in its center, with carbon and oxygen on both sides. Because oxygen is more electronegative than carbon, the electron cloud from both sides is pushed to oxygen, and both oxygen atoms have the same propensity, thus the net impact is zero.
Ans. The dipole moment () is calculated by multiplying the magnitude of the charge Q times the distance r between the charges. The dipole moment describes charge separation in a molecule.
Ans. The dipole moment occurs when the molecule involved in bonding has a substantial electronegativity difference between the two atoms. The greater the difference in electronegativity between two atoms in a molecule, the greater the polarity and dipole moment.
Ans. A dipole moment is a measure of the distance between two opposing electrical charges. Dipole moments are measured as vector quantities. The magnitude is equal to the charge multiplied by the distance between the charges, and the direction is positive charge to negative charge = q.r is the dipole moment, q is the magnitude of the separated charge, and r is the distance between the charges.