What is Percentage Ionic Character? How to Calculate it?
The percentage ionic character of a bond shows how much a bond is ionic. It's an important concept in understanding the nature of chemical bonds in compounds. The percentage ionic character can be calculated using the electronegativity difference of the bonded atoms. Higher the difference in electronegativity, higher the percentage of ionic character indicating the bond is more ionic.
Pauling Electronegativity Difference Method
Percentage Ionic Character = ( 1 − e− Δ𝜒2/4 ) × 100
Where, e is the base of the natural logarithm (approximately 2.718), Δ𝜒 is the electronegativity difference.
Hannay and Smith Electronegativity Difference Method
Percentage Ionic Character = [16 x Δ𝜒] + [3.5 x (Δ𝜒)2]
Dipole Moment Method
According to Henry-Smith formula, what is the percentage of ionic character in CsF [electronegativity of Cs = 0.7 and electronegativity of F = 4.0].
Answer
Percentage ionic character = (16 x 3.3) + 3.5 x (3.3)2
52.8 + 38.115 = 90.915
Bond distance in HF is 9.17 × 10−11 m. Dipole moment of HF is 6.104 × 10−30 cm. What would be the percentage of ionic character in HF?
Answer
Electron charge (e) = 1.60 × 10−19 C
d = 9.17 × 10−11 m
From µ = e × d
µ = 1.60 × 10−19 × 9.17 × 10−11
= 14.672 × 10−30
Percentage ionic character = Observed dipole moment/Dipole moment for 100% ionic bond
= [(6.104 x 10−30)/(14.672 x 10−30)] x 100
= 41.5%
Calculate the percentage of covalent character of HX having bond length = 1.62 Å and observed dipole moment = 0.39 D.
Answer
Calculated dipole moment = 4.8 x 10−10 esu x 1.62 x 10−8 cm = 7.776D.
Percentage Ionic Character = (0.39 x 100)/7.776 = 5%
Percentage Covalent Character = 100 − 5 = 95%
Percentage ionic character from Dipole Moment
Percentage ionic character:
Percentage ionic character from Electronegativity
Hannay and Smith Formula
Percentage ionic character:
Percentage ionic character from Dipole Moment
Percentage ionic character:
