2.2.6 Molecular Polarity
The vector sum of bond dipoles.
Determining Net Dipole
A molecule can contain polar bonds but still be non-polar overall if the bond dipoles cancel out due to symmetry.
Non-Polar Molecules
Usually occur when there are no lone pairs on the central atom and all outer atoms are identical.
Examples: CO₂ (Linear), BF₃ (Trigonal Planar), CH₄ (Tetrahedral), CCl₄.
Examples: CO₂ (Linear), BF₃ (Trigonal Planar), CH₄ (Tetrahedral), CCl₄.
Polar Molecules
Usually occur when there are lone pairs (breaking symmetry) or different outer atoms.
Examples: H₂O (Bent), NH₃ (Pyramidal), CH₃Cl.
Examples: H₂O (Bent), NH₃ (Pyramidal), CH₃Cl.