Electronegativity & Polarity Checker
Polarity Analysis
Enter a molecule
Check electronegativity differences and determine if a molecule is polar or nonpolar.
Molecule Database (30)
| Formula | Name | Polarity | Dipole | Geometry |
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Electronegativity & Polarity Guide
Pauling EN Scale
Electronegativity measures an atom's ability to attract electrons in a bond. Fluorine (3.98) is the most electronegative; cesium (0.82) is the least.
Bond Types by ΔEN
0.4 ≤ ΔEN < 1.7 — Polar Covalent (unequal sharing, e.g. O–H)
ΔEN ≥ 1.7 — Ionic (electron transfer, e.g. Na–Cl)
Molecular Polarity Rules
A molecule is nonpolar if all bond dipoles cancel by symmetry (identical terminal atoms, no lone pairs, and symmetric geometry). A molecule is polar if dipoles do not cancel due to asymmetric geometry, lone pairs, or mixed substituents.
Common Examples
Polar: H₂O (bent, 1.85 D), NH₃ (pyramidal, 1.47 D), HCl (linear, 1.09 D), CHCl₃ (tetrahedral, 1.04 D), SO₂ (bent, 1.63 D)
1 What is Electronegativity?
Electronegativity is a measure of an atom's ability to attract shared electrons in a chemical bond. The most widely used scale is the Pauling electronegativity scale, developed by Linus Pauling in 1932. Values range from 0.82 (cesium, least electronegative) to 3.98 (fluorine, most electronegative).
2 Pauling Electronegativity Scale
Key elements colored by their electronegativity value (blue = low, red = high):
3 Bond Types by ΔEN
Nonpolar Covalent
Equal sharing of electrons. Example: C–H (ΔEN = 0.35)
Polar Covalent
Unequal sharing. Example: O–H (ΔEN = 1.24)
Ionic
Electron transfer. Example: Na–Cl (ΔEN = 2.23)
4 How to Determine Molecular Polarity
Follow these four steps for any molecule. This is the exact process our checker automates:
Calculate ΔEN for each bond
Look up Pauling EN values for both atoms and compute the absolute difference. Classify as nonpolar covalent, polar covalent, or ionic.
Determine the molecular geometry
Use VSEPR theory to find the 3D shape. Count bonding pairs and lone pairs on the central atom.
Draw bond dipole vectors
Each polar bond has a dipole vector pointing from δ+ to δ−. The magnitude is proportional to ΔEN.
Check if dipoles cancel by symmetry
If all dipoles cancel (symmetric geometry, identical terminals, no lone pairs) → Nonpolar. Otherwise → Polar.
5 Dipole Moment Direction
A dipole moment is a vector quantity measured in Debye (D). It points from the center of positive charge toward the center of negative charge. For a single bond, it points from the less electronegative atom (δ+) to the more electronegative atom (δ−). The net molecular dipole moment is the vector sum of all individual bond dipoles.
6 Polar vs Nonpolar Examples
Polar Molecules
H₂O — Bent, 1.85 D. Two lone pairs create asymmetry.
NH₃ — Pyramidal, 1.47 D. One lone pair, dipoles don't cancel.
HCl — Linear diatomic, 1.09 D. Single bond dipole.
CHCl₃ — Tetrahedral, 1.04 D. Mixed substituents.
Nonpolar Molecules
CO₂ — Linear, 0 D. Opposing C=O dipoles cancel.
CH₄ — Tetrahedral, 0 D. Perfect symmetry.
CCl₄ — Tetrahedral, 0 D. Identical C–Cl bonds.
SF₆ — Octahedral, 0 D. Six identical bonds cancel.
7 Understanding the EN Heatmap
The EN Heatmap mode in the 3D viewer colors each atom by its Pauling electronegativity value using a blue–white–red gradient:
The Charge Map mode uses MMFF94 partial charges computed by PubChem. Red atoms carry partial negative charge (δ−, electron-rich), blue atoms carry partial positive charge (δ+, electron-poor). This shows the actual computed charge distribution, which can differ from simple EN predictions due to resonance and inductive effects.
8 Real-World Applications
Boiling Points
Polar molecules have stronger intermolecular forces (dipole-dipole, hydrogen bonding), leading to higher boiling points. Water (100°C) vs methane (−161°C).
Solubility
"Like dissolves like" — polar solvents dissolve polar solutes. NaCl dissolves in water but not in hexane. Oil (nonpolar) doesn't mix with water (polar).
Chemical Reactivity
Bond polarity determines reaction sites. Nucleophiles attack δ+ carbon in carbonyl groups. Electrophiles attack δ− oxygen or nitrogen lone pairs.
Biological Systems
Cell membranes use nonpolar lipid tails and polar head groups. Drug design requires matching polarity to cross membranes or dissolve in blood.