Question

Statement I : Dipole moment is a vector quantity and by convention it is depicted by a small arrow with tail on the negative centre and head pointing towards the positive centre
Statement II : The crossed arrow of the dipole moment symbolizes the direction of the shift of charges in the molecules.
In the light of the above statements, choose the most appropriate answer from the options given below:

• A. Both Statement I and Statement II are correct
• B. Statement I is correct but Statement II is incorrect
• C. Statement I is incorrect but Statement II is correct
• D. Both Statement I and Statement II are incorrect

Answer 1

The Correct Option is B

To analyze the correctness of the given statements about dipole moment, let's delve into each statement with an explanation of fundamental concepts related to dipole moment in chemistry. 

1. Statement I: "Dipole moment is a vector quantity and by convention it is depicted by a small arrow with tail on the negative centre and head pointing towards the positive centre"
   • This statement is indeed correct. In chemistry, the dipole moment is depicted as a vector arrow pointing from the negative charge center towards the positive charge center. This representation symbolizes that the electron density in a molecule is shifting from the more electronegative atom towards the less electronegative atom, creating a polarity.
   • The dipole moment (\( \mu \)) is calculated using the formula: \(\mu = q \times d\), where \( q \) is the magnitude of the charge and \( d \) is the distance between the charges.
   • The dipole moment is a vector quantity because it has both magnitude and direction.
2. Statement II: "The crossed arrow of the dipole moment symbolizes the direction of the shift of charges in the molecules"
   • This statement is incorrect. The crossed arrow convention used in the depiction of dipole moments arises from a physics convention where the crossed tail of the arrow symbolizes the positive side, and it is used to represent an electric dipole with vectors starting from the positive charge. However, in chemistry, the convention is reversed, and the arrowhead points towards the positive charge center instead.
   • This confusion seems to arise from the difference in conventions used in physics and chemistry.

Based on the analysis of each statement, the most appropriate answer is: Statement I is correct but Statement II is incorrect. Thus, the dipole moment as a vector is depicted with its tail on the negative center, and the head pointing towards the positive center, while the statement concerning the crossed arrow erroneously implies a representation opposite to the accepted chemical convention.