Understanding Conductivity

* Ionic Compounds: Ionic compounds are excellent conductors when molten or dissolved in water because their ions are free to move and carry an electric current.

* Covalent Compounds: Covalent compounds generally do not conduct electricity in their pure liquid or molten state. This is because they exist as molecules, not ions.

Analyzing the Compounds

Let's examine each compound:

1. I₂ (Iodine): Non-polar covalent, poor conductor.

2. H₂S (Hydrogen sulfide): Polar covalent, poor conductor.

3. AsH₃ (Arsine): Polar covalent, poor conductor.

4. SiH₄ (Silane): Non-polar covalent, poor conductor.

5. H₂Se (Hydrogen selenide): Polar covalent, poor conductor.

6. H₂Te (Hydrogen telluride): Polar covalent, poor conductor.

7. BaF₂ (Barium fluoride): Ionic compound, excellent conductor when molten.

8. GeH₄ (Germane): Non-polar covalent, poor conductor.

9. NH₃ (Ammonia): Polar covalent, poor conductor.

10. Cl₂ (Chlorine): Non-polar covalent, poor conductor.

Conclusion

The best conductor in its pure liquid or molten state is BaF₂ (Barium fluoride). This is because it's an ionic compound, and its ions will be free to move and carry an electric current when the compound is molten.