Which of the following is an indication of the strength of the force of attraction between particles of solid state?

Melting point

The correct answer is option 2. Melting point.

The indication of the strength of the force of attraction between particles in the solid state is the Melting point. The melting point is the temperature at which a solid substance changes from a solid to a liquid. The strength of the force of attraction between particles (molecules or atoms) in a solid affects the temperature at which the substance melts. Substances with strong intermolecular forces will generally have higher melting points, while those with weaker forces will have lower melting points. The boiling point and isoelectric point are related to different properties and phenomena and are not direct indicators of the strength of intermolecular forces in the solid state.