To determine the nature of each compound given their properties, let's analyze each one step-by-step:
### Compound 1:
1. Description: It's a yellow solid made up of clusters of needle-like crystals.
2. Electrical Properties: It's a good electrical insulator when solid but becomes a good conductor when dissolved in water.
Analysis:
- Solids that don't conduct electricity but do when dissolved in water or melted are typically ionic compounds. This is because ionic compounds consist of ions held together in a lattice. In solid form, the ions are not free to move and thus do not conduct electricity. However, when dissolved in water, the ions dissociate and move freely, allowing the solution to conduct electricity.
Conclusion: Compound 1 is likely an ionic compound.
### Compound 2:
1. Description: It's a deep red solid with a noticeable unpleasant smell.
2. Solubility and Electrical Conductivity: It dissolves slightly in water, but a solution of 2 g in 100 mL of water doesn't change the electrical conductivity of the water.
Analysis:
- Compounds that dissolve in water without changing the electrical conductivity typically do not produce ions in solution. This characteristic is typical of molecular compounds because they consist of molecules that remain intact upon dissolving in water, not producing ions.
Conclusion: Compound 2 is likely a molecular compound.
### Compound 3:
1. Description: It's a hard grayish-white solid. When tapped gently with a small hammer, it fractures into fragments and a whitish powder.
2. Solubility and Electrical Conductivity: The powder is soluble in water, and when dissolved in water, the solution conducts electricity well.
Analysis:
- The ability of a solution to conduct electricity well after dissolving a compound into it indicates the presence of ions in the solution. Therefore, this behavior is characteristic of ionic compounds.
Conclusion: Compound 3 is likely an ionic compound.
### Final Results:
Based on the detailed analysis, the nature of each compound can be summed up as:
- Compound 1: Ionic
- Compound 2: Molecular
- Compound 3: Ionic
Therefore, the final answer is:
[tex]\[
\text{(1, 2, 1)}
\][/tex]
