What is the size of the particles of a true solution?

Less than 1 nm in diameter

The correct answer is option 1. Less than 1 nm in diameter.

In a true solution, the solute particles are individual molecules or ions dispersed uniformly in the solvent at the molecular level. These particles are extremely small, and their size is typically measured in nanometers (nm).

Less than 1 nm in diameter: The statement "Less than 1 nm in diameter" means that the size of the solute particles in a true solution is smaller than one nanometer. To provide some perspective, 1 nanometer is equivalent to 1 billionth of a meter.

Molecular and Ionic Size:  The solute particles in a true solution are on the scale of molecules or ions. These particles are so small that they do not scatter light, and they remain in a homogeneous mixture with the solvent, forming a clear and transparent solution.

This characteristic distinguishes true solutions from colloids and suspensions, where the particle sizes are larger and may be visible under certain conditions. True solutions exhibit the unique property of passing through filters and membranes due to the extremely small size of their particles.