How Is Fractional Charge Calculated in Diatomic Molecules?

[physgirl]

Homework Statement

For this problem, I had to find the fractional charge given the dipole moment u and bond length R in a diaomic molecule (H-X, where X is a halogen)... I found that fractional charge by: fractional charge=u/(eR)
where e=elementary charge of an electron

I think that's correct?? So then using that, I said that percent ionic character in the bond is "fractional charge"*100%.

So then to find the effective fractional charge on the H and X atom, is that just +"fractional charge" on the H and -"fractional charge" on X?



So in short, if I found fractional charge between HCl to be 0.18 (would it be ok to do that by doing fractional charge=u/(eR)?), for instance, then percent ionic character would be 18% and effective fractional charge on H would be +0.18 and that on Cl would be -0.18?

 

[Gokul43201]

Looks good. As a doublecheck, you can compare with the % ionic character computed from the electronegativity difference.

 

[Blueshift5]

I can say that your calculations and reasoning are correct. The concept of dipole and fractional charge is an important one in chemistry, particularly in understanding the nature of chemical bonds. A dipole moment is a measure of the separation of positive and negative charges in a molecule. In a molecule like H-X, where X is a halogen, the bond between the two atoms is polar, meaning that there is a difference in electronegativity between the two atoms. This results in a dipole moment, with the more electronegative atom having a partial negative charge and the less electronegative atom having a partial positive charge.

Your calculation of fractional charge using the formula u/(eR) is correct. This represents the fractional charge on each atom in the molecule. In the case of H-X, the effective fractional charge on H would be +0.18 and on X would be -0.18. This represents the distribution of charge in the molecule and is important in understanding the chemical properties and reactivity of the molecule.

Additionally, your calculation of percent ionic character is also correct. This represents the degree of ionic character in the bond, with a higher percentage indicating a more polar bond. In this case, the percent ionic character is 18%.

Overall, your understanding and application of the concept of dipole and fractional charge is correct and shows a good grasp of the fundamental principles of chemistry. Keep up the good work in your studies!