Electrostatic Potential Maps from Hartree-Fock Calculations (3-21G*)

CH₄

HF

H₂O

NH₃

BeH₂

BH₃

H₂

LiH

Electrostatic Potential Maps from Hartree-Fock Calculations (3-21G*)

Bond	Difference in Electronegativity	Electrostatic Charge on H
	(X - H)	(Max in Potential Surface)
H-H	0	0
Li-H	-1.2	-0.7
Be-H	-0.6	-0.3
B-H	-0.2	-0.2
C-H	0.4	0.1
N-H	0.8	0.43
O-H	1.2	0.44
F-H	1.8	0.49

What electronegativity difference, large or small, creates a more polar bond?
A more covalent bond?

Is the difference in electronegativity a reasonable way to estimate the polarity of bonds?