SF5- is polar or non polar
The correct answer and explanation is:
Answer: SF₅⁻ (the pentafluorosulfanyl anion) is polar.
Explanation:
To determine whether SF₅⁻ is polar or nonpolar, we need to analyze its molecular geometry and the distribution of charge.
1. Molecular Formula and Geometry:
- SF₅⁻ consists of one sulfur (S) atom bonded to five fluorine (F) atoms, with an overall negative charge.
- Sulfur has 6 valence electrons, each fluorine has 7, and there is an extra electron due to the negative charge.
- Total valence electrons = 6 (S) + 5 × 7 (F) + 1 (charge) = 6 + 35 + 1 = 42 electrons.
2. Electron Pair Geometry:
- Sulfur typically expands its octet and can accommodate more than 8 electrons.
- SF₅⁻ has 5 bonding pairs (S-F bonds) and 1 lone pair on sulfur.
- This results in 6 electron domains around sulfur.
- According to VSEPR theory, 6 electron domains correspond to an octahedral electron pair geometry.
- With 5 bonding pairs and 1 lone pair, the molecular shape is a square pyramidal structure.
3. Effect of Geometry on Polarity:
- A perfect octahedral molecule with 6 identical atoms around the central atom (e.g., SF₆) is nonpolar because the bond dipoles cancel out due to symmetry.
- However, in SF₅⁻, one position is occupied by a lone pair, not a fluorine atom.
- This lone pair distorts the symmetry, making the molecule asymmetric.
- The asymmetry prevents the dipole moments from canceling out.
4. Electronegativity Considerations:
- Fluorine is highly electronegative, pulling electron density toward itself.
- The lone pair on sulfur also influences the electron density distribution.
- The negative charge is likely localized near the sulfur atom and lone pair region.
- This uneven distribution creates a net dipole moment.
Conclusion:
The presence of a lone pair on sulfur distorts the symmetry of the otherwise octahedral SF₆ structure, resulting in a square pyramidal geometry for SF₅⁻. This asymmetric shape combined with differences in electronegativity and electron distribution leads to a polar molecule. Therefore, SF₅⁻ is polar.