Which one of the following molecules is nonpolar? SOF2 AsF3 NO2Br SF6 SO
The correct answer and explanation is:
The correct answer is: SF₆ (sulfur hexafluoride)
Explanation (Approximately 300 words):
To determine which molecule is nonpolar, we must analyze both the electronegativity of the atoms and the molecular geometry (shape).
1. Polarity Basics:
- A polar molecule has an uneven distribution of electrons, leading to a dipole moment (one end slightly positive, the other slightly negative).
- A nonpolar molecule either has no dipole moment or has dipoles that cancel out due to molecular symmetry.
2. Analysis of the Molecules:
- SOF₂ (Thionyl fluoride): This molecule has a bent or trigonal pyramidal shape because of the lone pairs on sulfur. The F and O atoms have different electronegativities and are positioned asymmetrically, making the molecule polar.
- AsF₃ (Arsenic trifluoride): Has a trigonal pyramidal shape due to a lone pair on arsenic. The bond dipoles do not cancel, so the molecule is polar.
- NO₂Br (Nitrogen dioxide bromide): This molecule is asymmetrical with different atoms (O and Br) bonded to nitrogen. It has an uneven distribution of charge and is therefore polar.
- SF₆ (Sulfur hexafluoride): Sulfur is surrounded by six fluorine atoms in an octahedral geometry. Even though the S–F bonds are polar, the molecule is highly symmetrical, so all the dipoles cancel out. This makes SF₆ a nonpolar molecule despite having polar bonds.
- SO (Sulfur monoxide): This is a diatomic molecule with polar bonds (oxygen is more electronegative), and there is no symmetry to cancel out the dipole. Thus, SO is polar.
3. Conclusion:
SF₆ is nonpolar because of its perfectly symmetrical octahedral structure, which causes the bond dipoles to cancel out, resulting in no overall molecular dipole moment. All other choices have either asymmetrical structures or different electronegativities in positions that don’t cancel dipoles, making them polar.