Nonzero Dipole Moment

Introduction
In chemistry, the dipole moment is a measure of the polarity of a chemical bond or a molecule. It is a vector quantity that indicates the separation of positive and negative charges within a molecule. A molecule with a nonzero dipole moment means it has an asymmetrical distribution of charge, resulting in a polar molecule. On the other hand, a molecule with a zero dipole moment is symmetrical and nonpolar.

Explanation of Nonzero Dipole Moment
Out of the given options, the following molecules have a nonzero dipole moment:

1. H2O (Water)
2. NH3 (Ammonia)
3. CHCl3 (Chloroform)
4. SO2 (Sulfur Dioxide)

1. H2O (Water)
- Water is a bent molecule with two lone pairs of electrons on the oxygen atom and two hydrogen atoms.
- Due to the electronegativity difference between oxygen and hydrogen, the oxygen atom pulls the shared electrons closer to itself, creating a partial negative charge (δ-) on the oxygen and a partial positive charge (δ+) on the hydrogens.
- This unequal charge distribution leads to a dipole moment, making water a polar molecule.

2. NH3 (Ammonia)
- Ammonia molecule consists of a nitrogen atom bonded to three hydrogen atoms.
- Nitrogen is more electronegative than hydrogen, so it attracts the shared electrons closer to itself.
- This results in a partial negative charge (δ-) on the nitrogen atom and partial positive charges (δ+) on the hydrogens.
- The asymmetrical charge distribution gives ammonia a dipole moment, making it a polar molecule.

3. CHCl3 (Chloroform)
- Chloroform contains a central carbon atom bonded to three hydrogen atoms and a chlorine atom.
- Chlorine is more electronegative than carbon and hydrogen, causing the electrons to be pulled closer to the chlorine atom.
- As a result, the chlorine atom acquires a partial negative charge (δ-), and the carbon and hydrogen atoms have partial positive charges (δ+).
- This uneven charge distribution leads to a nonzero dipole moment, making chloroform a polar molecule.

4. SO2 (Sulfur Dioxide)
- Sulfur dioxide consists of a central sulfur atom bonded to two oxygen atoms.
- The oxygen atoms are more electronegative than sulfur, causing them to pull the shared electrons closer to themselves.
- This creates a partial negative charge (δ-) on the oxygen atoms and a partial positive charge (δ+) on the sulfur atom.
- The unequal charge distribution results in a dipole moment, making sulfur dioxide a polar molecule.

Summary
In summary, the molecules H2O (water), NH3 (ammonia), CHCl3 (chloroform), and SO2 (sulfur dioxide) have a nonzero dipole moment due to their asymmetrical charge distribution. These molecules are considered polar since they have a separation of positive and negative charges, resulting in a dipole moment.