Molecular Solids

Molecular solids are composed of individual molecules held together by intermolecular forces. These types of solids typically have low melting and boiling points and are poor conductors of heat and electricity.

Examples of Molecular Solids

a) Sic - Not a Molecular Solid
Sic, or silicon carbide, is a covalent network solid consisting of atoms covalently bonded in a three-dimensional network. It does not have individual molecules held together by intermolecular forces, so it is not a molecular solid.

b) CaF2 - Not a Molecular Solid
CaF2, or calcium fluoride, is an ionic compound consisting of positively charged calcium ions and negatively charged fluoride ions held together by ionic bonds. It does not have individual molecules held together by intermolecular forces, so it is not a molecular solid.

c) SiO2 - Not a Molecular Solid
SiO2, or silicon dioxide, is a covalent network solid consisting of atoms covalently bonded in a three-dimensional network. It does not have individual molecules held together by intermolecular forces, so it is not a molecular solid.

d) CH4 - Molecular Solid
CH4, or methane, is a molecular solid consisting of individual molecules held together by weak intermolecular forces. It has a low melting and boiling point and is a poor conductor of heat and electricity, which are characteristics of molecular solids.

Conclusion

Out of the given options, CH4 is the only example of a molecular solid. The other options either consist of covalent network solids or ionic compounds, which do not have individual molecules held together by intermolecular forces.

Calcium fluoride (CaF2) is ionic crystals due to presence of ionic bond in them.
Silicon dioxide (SiO2) & Silicon carbide (SiC) are network solid due to strong intermolecular covalent bond.

So, correct answer is CH4...

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