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Is HI Polar or Nonpolar?
Hydrogen iodide is polar because iodine (2.66) is more electronegative than hydrogen (2.20). The small electronegativity difference of 0.46 gives HI the smallest dipole moment in the hydrogen halide series (0.45 D), making it the least polar of HF, HCl, HBr, and HI.
Why is HI Polar?
Hydrogen iodide is polar because iodine (2.66) is more electronegative than hydrogen (2.20). The small electronegativity difference of 0.46 gives HI the smallest dipole moment in the hydrogen halide series (0.45 D), making it the least polar of HF, HCl, HBr, and HI.
- Electronegativity difference: I (2.66) is significantly more electronegative than H (2.2), creating partial charges on each atom and making the individual bonds polar.
- Linear shape (—): The asymmetric molecular geometry means the bond dipoles point in directions that do not cancel — they add up to produce a net dipole moment of 0.45 D.
- Net dipole moment (0.45 D): Any molecule with a nonzero net dipole moment is classified as polar. The 0.45 D dipole moment of HI confirms its polar character.
Molecular Geometry of HI
HI has a linear molecular geometry with a bond angle of —. Here is why this shape determines polarity:
- The central atom's electron pairs arrange themselves to minimize repulsion, resulting in the linear shape.
- The — bond angle creates an asymmetric arrangement — the bond dipoles point in directions that do not perfectly oppose each other.
- Asymmetry is the key: if HI had a perfectly symmetric geometry, its bond dipoles would cancel and the molecule would be nonpolar. The linear shape prevents this cancellation.
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 HI:
- H (central atom) electronegativity: 2.2
- I (outer atom) electronegativity: 2.66
- Difference: 0.46 — below the ~0.5 threshold, so the H–I bonds are only weakly polar
The combination of polar bonds and an asymmetric linear geometry means the partial charges do not cancel — making HI a polar molecule with a net dipole of 0.45 D.
Is HI Polar or Nonpolar? (Quick Answer)
HI (Hydrogen Iodide) is polar. HI is polar because iodine is more electronegative than hydrogen, though the small difference results in the weakest dipole (0.45 D) among the hydrogen halides.
Frequently Asked Questions
Is HI polar or nonpolar?
HI is polar because iodine is more electronegative than hydrogen, though the small difference results in the weakest dipole (0.45 D) among the hydrogen halides.
Why is Hydrogen Iodide polar?
Hydrogen iodide is polar because iodine (2.66) is more electronegative than hydrogen (2.20). The small electronegativity difference of 0.46 gives HI the smallest dipole moment in the hydrogen halide series (0.45 D), making it the least polar of HF, HCl, HBr, and HI.
What is the shape of HI?
HI has a linear molecular geometry with a bond angle of —. This shape results in an asymmetric charge distribution and a net dipole moment of 0.45 D, making the molecule polar.
Does HI have a dipole moment?
Yes. HI has a dipole moment of 0.45 D. Its linear geometry and polar bonds combine to produce a net dipole, confirming its polar character.