Is CS2 polar or nonpolar? NOBr Polar or Nonpolar
The Correct Answer and Explanation is:
Carbon disulfide (CS₂): Nonpolar
Nitrosyl bromide (NOBr): Polar
Carbon Disulfide (CS₂) – Nonpolar
Carbon disulfide (CS₂) is a linear molecule composed of one carbon atom double-bonded to two sulfur atoms (S=C=S). Although the C=S bonds are polar due to a difference in electronegativity between carbon (2.55) and sulfur (2.58), the molecule’s symmetrical linear shape causes the individual bond dipoles to cancel each other out. This results in a net dipole moment of zero, making CS₂ a nonpolar molecule.
Nonpolarity in molecules occurs when:
- The molecule has symmetrical geometry.
- Bond dipoles cancel each other due to equal magnitude and opposite direction.
In CS₂, both sulfur atoms pull electrons equally and symmetrically away from the carbon. Despite the slightly polar nature of each bond, the linear symmetry ensures that the vector sum of dipole moments is zero.
Nitrosyl Bromide (NOBr) – Polar
NOBr is a bent or angular molecule made up of a nitrogen atom bonded to both an oxygen and a bromine atom. Oxygen is more electronegative than nitrogen (O: 3.44, N: 3.04), and nitrogen is more electronegative than bromine (Br: 2.96). This creates a significant difference in bond polarities:
- The N=O bond is polar with electron density pulled toward oxygen.
- The N–Br bond is also polar, with a smaller dipole toward nitrogen.
The bent molecular geometry (due to the presence of a lone pair on nitrogen) means that these dipole moments do not cancel. Instead, they add up to form a net dipole moment, making NOBr a polar molecule.
Polarity arises in NOBr because of:
- Uneven distribution of electron density.
- Asymmetrical (bent) molecular geometry.
- Unequal bond polarities that do not cancel.
Thus, CS₂ is nonpolar due to symmetry, while NOBr is polar due to its bent shape and unequal bond dipoles.
