Is a Molecule Polar or Non-Polar?

These are problems enhanced with 3D molecules run in the application Jmol to help you determine if a molecule is polar or non-polar.

Step 1: Draw the Lewis structure. Step 2: Use this to determine the 3D geometry of the molecule. You do this be remembering "VSEPR". Valence shell electron pair repulsion theory; around the central atom all regions of electrons repel each other to get as far away from each other as possible while pivoting around the central atom. Note that double bonds and triple bonds count as a single region of electrons. Step 3: Determine if the molecular is polar or non-polar.

After you have drawn a 3D representation of your molecule, if the molecule has sufficient symmetry, the bond dipole moments will cancel out (due to symmetric charge distribution) and the molecule will be non-polar.

However, if the molecule does not have sufficient symmetry, the bond dipole moments will not cancel out (unsymmetric charge distribution) and the molecule will have a net dipole moment (the molecule is therefore polar).

To really understand how to do this, the Lewis structure is only the first step. You need to consider the molecule in 3D (three dimensions). If you click on the example molecules (where it says 3D view) below you'll get a better understanding of why some molecules are polar and some not.

Note: molecules with two atoms are not shown in these examples; they are always linear with sp hybridization. If the atoms are the same, the molecule is non-polar molecule; if the atoms are different, the molecule is polar.

Summary: Table of Molecular Geometry, 3D Molecule Samples (You can rotate the molecules), Molecular Polarity Problems (with 3D solutions!).

Summary:


The Relationship Between the Number of Regions of Valence Electrons and the Molecular Geometry Around an Atom. Click for Print View.


Total Electron Regions	Bonding Electron Regions	Lone Pair Regions	Distribution of Electrons	Molecular Geometry	Examples

2	2	0	linear	linear	BeF₂, CO₂
	1	1		linear	CO, N₂

3	3	0	trigonal planar	trigonal planar	BF₃, CO₃^2-
	2	1		bent	O₃, SO₂
	1	2		linear	O₂

4	4	0	tetrahedral	tetrahedral	CH₄, SO₄^2-
	3	1		trigonal pyramidal	NH₃, H₃O⁺
	2	2		bent	H₂O, ICl₂⁺
	1	3		linear	HF, OH^-

5	5	0	trigonal bipyramidal	trigonal bipyramidal	PF₅
	4	1		seesaw	SF₄, TeCl₄, IF₄⁺
	3	2		T-shaped	ClF₃
	2	3		linear	I₃^-, XeF₂

6	6	0	octahedral	octahedral	SF₆, PF₆^-, SiF₆^2-
	5	1		square pyramidal	BrF₅, SbCl₅^2-
	4	2		square planar	XeF₄, ICl₄^-

Valence Electron Pairs	Electron Pair Geometry	Bond Pairs	Lone Pairs	Molecular Geometry	Hybridization	Example Click and drag to rotate molecule.
Valence Electron Pairs: 2	Electron Pair Geometry:	Bond Pairs: 2	Lone Pairs: 0	Molecular Geometry	Hybridization: sp	BeCl₂ - symmetric; non-polar Click and drag to rotate molecule.

Valence Electron Pairs: 3	Electron Pair Geometry:	Bond Pairs: 3	Lone Pairs: 0	Molecular Geometry	Hybridization: sp²	BF₃ - symmetric; non-polar Click and drag to rotate molecule.
Valence Electron Pairs: 3	Electron Pair Geometry:	Bond Pairs: 2	Lone Pairs: 1	Molecular Geometry	Hybridization: sp²	SO₂ - asymmetric; polar Click and drag to rotate molecule.

Valence Electron Pairs: 4	Electron Pair Geometry:	Bond Pairs: 4	Lone Pairs: 0	Molecular Geometry	Hybridization: sp³	CCl₄ - symmetric; non-polar Click and drag to rotate molecule.
		Bond Pairs: 3	Lone Pairs: 1	Molecular Geometry		NH₃ - asymmetic; polar Click and drag to rotate molecule.
		Bond Pairs: 2	Lone Pairs: 2	Molecular Geometry		H₂O - asymmetic; polar Click and drag to rotate molecule.

Valence Electron Pairs: 5	Electron Pair Geometry:	Bond Pairs: 5	Lone Pairs: 0	Molecular Geometry	Hybridization: sp³d	PF₅ - symmetic; non-polar Click and drag to rotate molecule.
		Bond Pairs: 4	Lone Pairs: 1	Molecular Geometry		SF₄ - asymmetic; polar Click and drag to rotate molecule.
		Bond Pairs: 3	Lone Pairs: 2	Molecular Geometry		BrCl₃ - asymmetic; polar Click and drag to rotate molecule.
		Bond Pairs: 2	Lone Pairs: 3	Molecular Geometry		XeF₂ - symmetric; non-polar Click and drag to rotate molecule.

Valence Electron Pairs: 6	Electron Pair Geometry:	Bond Pairs: 6	Lone Pairs: 0	Molecular Geometry	Hybridization: sp³d²	SF₆ - symmetric; non-polar Click and drag to rotate molecule.
		Bond Pairs: 5	Lone Pairs: 1	Molecular Geometry		BrF₅ - asymmetric; polar Click and drag to rotate molecule.
		Bond Pairs: 4	Lone Pairs: 2	Molecular Geometry		XeF₄ - symmetric; non-polar Click and drag to rotate molecule.