Electrostatic Maps
Visualization of electron density and charge distribution in molecules. Covers polar vs nonpolar bonds, net dipole moments, and the spectrum from ionic to covalent bonding character.
CH₄: uniform charge (nonpolar)
H₂O: O is δ⁻ (red), H is δ⁺ (blue)
Methane is nonpolar despite having slightly polar C-H bonds. The symmetric tetrahedral geometry causes all four bond dipoles to cancel exactly, resulting in zero net dipole moment.
Water has a large dipole moment (1.85 D) because its bent geometry prevents the two O-H bond dipoles from canceling. The oxygen atom carries a partial negative charge while the hydrogens carry partial positive charges.
Cl₂: nonpolar bond (equal sharing)
HCl: polar bond (H δ⁺, Cl δ⁻)
Cl2 has a perfectly nonpolar bond because both atoms have identical electronegativity. The electrons are shared equally with no charge separation. This is why Cl2 is a gas at room temperature with weak London dispersion forces only.
HCl has a polar bond because chlorine (EN = 3.16) is more electronegative than hydrogen (EN = 2.20). The electronegativity difference of 0.96 creates a partial negative charge on chlorine and a partial positive charge on hydrogen.
CO₂: symmetric, no net dipole
H₂O: bent, net dipole moment
Although CO2 has two polar C=O bonds, the linear geometry (180 degrees) causes the bond dipoles to point in exactly opposite directions, canceling completely. CO2 has zero net dipole moment and is a nonpolar molecule.
Water's bent geometry (104.5 degrees) means the two O-H bond dipoles add up to a net dipole pointing from the hydrogens toward the oxygen. This makes water an excellent polar solvent with a high dielectric constant.
HF: partial charge (polar covalent)
NaCl: full charge separation (ionic)
HF has significant polarity (EN difference of 1.78) but remains a polar covalent molecule. The electrons are unequally shared rather than fully transferred. HF exists as discrete molecules in the gas phase, unlike the extended lattice of NaCl.
NaCl has a large electronegativity difference (2.23) resulting in nearly complete electron transfer from sodium to chlorine. The Na+ cation and Cl- anion are held together by electrostatic attraction, making NaCl a classic ionic compound.