Question
The dipole moment of hydrogen halides decreases from HF to HI. Explain this trend.
Solution
The Ionic character in a covalent bond depends on upon the difference between the electronegativity of the two atoms. Greater the electronegativity difference, greater is the charge separation and therefore, greater is the ionic character in the bond.
In H-X, X (F,Cl, Br, I) atom is more electronegative than H. Therefore,the H-X bond is polar and the direction of the dipole is from H to X. As the electronegativity of X decreases from F to I the charge separation decreases. Therefore, the dipole moment decreases.
For example, the dipole moment of hydrogen halides follow the order:
H - F > H - Cl > H -Br > H - I
Electro- 1 - 9 1-1 0-9 0- 6 ‘ negativity difference.
Dipole- 1-91 1-07 0-79 0-38 moment (D).
In H-X, X (F,Cl, Br, I) atom is more electronegative than H. Therefore,the H-X bond is polar and the direction of the dipole is from H to X. As the electronegativity of X decreases from F to I the charge separation decreases. Therefore, the dipole moment decreases.
For example, the dipole moment of hydrogen halides follow the order:
H - F > H - Cl > H -Br > H - I
Electro- 1 - 9 1-1 0-9 0- 6 ‘ negativity difference.
Dipole- 1-91 1-07 0-79 0-38 moment (D).
