Molecules in solids are solids are held together by dipole-dipole interactions. Identify the polar molecules from the following:

A. Solid \(SO_2\)

B. \(NH_3\)

C. \(Cl_2\)

D. \(HCl\)

E. \(He\)

Choose the correct answer from the options given below:

A, B and D only

The correct answer is option 1. A, B and D only.

Let us go through each molecule in detail to understand their polarity:

A. Solid \(SO_2\) (Sulfur Dioxide)

\(SO_2\) has a bent or V-shaped molecular geometry. This is due to the presence of one lone pair on the sulfur atom and the two bond pairs with oxygen atoms.

Polarity: The bent shape results in an asymmetric distribution of charge. The sulfur-oxygen bonds are polar due to the difference in electronegativity between sulfur and oxygen, leading to a net dipole moment in the molecule. Therefore, \(SO_2\) is a polar molecule.

Interactions: In the solid phase, \(SO_2\) molecules interact via dipole-dipole interactions due to their permanent dipole moments.

B. \(NH_3\) (Ammonia)

\(NH_3\) has a trigonal pyramidal molecular geometry. This shape is due to the lone pair of electrons on the nitrogen atom, which pushes the hydrogen atoms down.

Polarity: The nitrogen-hydrogen bonds are polar because nitrogen is more electronegative than hydrogen. The lone pair on nitrogen creates a net dipole moment pointing towards the nitrogen. Thus, \(NH_3\) is a polar molecule.

Interactions: In the solid phase, \(NH_3\) molecules interact via dipole-dipole interactions and hydrogen bonding due to the strong dipole moment.

C. \(Cl_2\) (Chlorine Gas)

\(Cl_2\) is a diatomic molecule with a linear shape where two chlorine atoms are bonded together.

Polarity: Both chlorine atoms have the same electronegativity, meaning they share electrons equally, resulting in no net dipole moment. Thus, \(Cl_2\) is a nonpolar molecule.

Interactions: In its solid form, \(Cl_2\) interacts via London dispersion forces (a type of van der Waals force), not dipole-dipole interactions.

D. \(HCl\) (Hydrochloric Acid)

\(HCl\) is a diatomic molecule with a linear shape.

Polarity: Hydrogen and chlorine have different electronegativities, with chlorine being more electronegative. This difference leads to a polar covalent bond with a dipole moment pointing towards chlorine. Therefore, \(HCl\) is a polar molecule.

Interactions: In its solid form, \(HCl\) molecules would interact via dipole-dipole interactions due to their permanent dipole moments.

E. \(He\) (Helium)

Helium is a noble gas with a simple atomic structure.

Polarity: Being a noble gas with a complete electron shell, helium has no permanent dipole moment. Therefore, it is nonpolar.

Interactions: In its solid form, \(He\) interacts via London dispersion forces.

Summary

From the above details, the polar molecules among the given options are:

Solid \(SO_2\): Polar

\(NH_3\): Polar

\(HCl\): Polar

Nonpolar molecules include:

\(Cl_2\): Nonpolar

\(He\): Nonpolar

Thus, the correct answer is: 1. A, B and D only