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Is AlCl3 Polar or Nonpolar?
Aluminum trichloride (in gas phase) has a trigonal planar geometry with no lone pairs on aluminum. Each Al–Cl bond is highly polar (Cl at 3.16 vs Al at 1.61), but the three bonds are arranged at equal 120° angles. Their dipoles cancel completely, giving AlCl3 a net dipole of 0 D.
Why is AlCl3 Nonpolar?
Aluminum trichloride (in gas phase) has a trigonal planar geometry with no lone pairs on aluminum. Each Al–Cl bond is highly polar (Cl at 3.16 vs Al at 1.61), but the three bonds are arranged at equal 120° angles. Their dipoles cancel completely, giving AlCl3 a net dipole of 0 D.
- Symmetric trigonal planar geometry (120°): The atoms are arranged symmetrically around the central atom. This forces all bond dipoles to point in directions that cancel each other out exactly.
- Polar bonds that cancel: The electronegativity difference between Cl (3.16) and Al (1.61) creates polar bonds — but the trigonal planar shape ensures their dipoles cancel perfectly.
- Zero net dipole (0 D): Because all bond dipoles cancel, the net dipole moment is 0 D. Any molecule with zero net dipole moment is classified as nonpolar.
Molecular Geometry of AlCl3
AlCl3 has a trigonal planar molecular geometry with a bond angle of 120°. Here is why this shape determines polarity:
- The trigonal planar arrangement places all outer atoms at equal angles (120°) from the central atom, creating perfect spatial symmetry.
- Each bond dipole has an equal and opposite counterpart — they cancel in pairs, leaving no net charge separation.
- Symmetry is the key: even if the individual bonds are polar, the trigonal planar geometry ensures a net dipole of 0 D.
Electronegativity and Polarity
Electronegativity measures how strongly an atom attracts bonding electrons. A difference greater than ~0.5 on the Pauling scale generally means the bond is polar.
In AlCl3:
- Al (central atom) electronegativity: 1.61
- Cl (outer atom) electronegativity: 3.16
- Difference: 1.55 — above the ~0.5 threshold, so the Al–Cl bonds are polar
Even though the individual bonds are polar (difference = 1.55), the trigonal planar geometry of AlCl3 causes them to cancel completely. Polarity depends on both bond polarity AND molecular shape.
Is AlCl3 Polar or Nonpolar? (Quick Answer)
AlCl3 (Aluminum Trichloride) is nonpolar. AlCl3 is a nonpolar molecule because its trigonal planar geometry causes the three polar Al–Cl bond dipoles to cancel symmetrically.
Frequently Asked Questions
Is AlCl3 polar or nonpolar?
AlCl3 is a nonpolar molecule because its trigonal planar geometry causes the three polar Al–Cl bond dipoles to cancel symmetrically.
Why is Aluminum Trichloride nonpolar?
Aluminum trichloride (in gas phase) has a trigonal planar geometry with no lone pairs on aluminum. Each Al–Cl bond is highly polar (Cl at 3.16 vs Al at 1.61), but the three bonds are arranged at equal 120° angles. Their dipoles cancel completely, giving AlCl3 a net dipole of 0 D.
What is the shape of AlCl3?
AlCl3 has a trigonal planar molecular geometry with a bond angle of 120°. This shape causes all bond dipoles to cancel perfectly, giving a net dipole of 0 D and making the molecule nonpolar.
Does AlCl3 have a dipole moment?
No. AlCl3 has a dipole moment of 0 D. Its trigonal planar geometry causes all individual bond dipoles to cancel out completely, resulting in a nonpolar molecule.