Low melting point is expected for a solid :

Options

A. Ionic solid
B. Metallic solid
C. Molecular solid
D. Covalent solid

Explanation

To determine which type of solid has a low melting point among the given options, we can analyze the characteristics of each type of solid:

1. **Ionic Solid**: Ionic solids are formed by the electrostatic attraction between positively and negatively charged ions. This strong ionic bonding results in high melting points. Examples include sodium chloride (NaCl) and magnesium oxide (MgO). Therefore, ionic solids are not expected to have low melting points.

2. **Metallic Solid**: Metallic solids consist of metal atoms that are held together by metallic bonds, which involve a sea of delocalized electrons. While metallic solids can have varying melting points, many have relatively high melting points due to the strength of metallic bonding. Thus, metallic solids are also not expected to have low melting points.

3. **Molecular Solid**: Molecular solids are composed of molecules held together by weaker intermolecular forces, such as Van der Waals forces or hydrogen bonds. These forces are significantly weaker than ionic or covalent bonds, which results in lower melting points. Examples include ice (solid water) and solid carbon dioxide (dry ice). Therefore, molecular solids are expected to have low melting points.

4. **Covalent Solid**: Covalent solids, also known as network solids, consist of atoms connected by covalent bonds in a continuous network. This strong bonding leads to very high melting points. Examples include diamond and silicon carbide. Hence, covalent solids are not expected to have low melting points.

Based on this analysis, the type of solid that is expected to have a low melting point is:

**Answer**: Molecular solid (Option 3).