Here's why:

* Heavy metals are typically dense metals that are toxic in high concentrations. They often have a high atomic weight.

* Silver nitrate, mercurochrome, merthiolate, and copper sulfate all contain heavy metals:

* Silver nitrate contains silver.

* Mercurochrome and merthiolate both contain mercury.

* Copper sulfate contains copper.

Chlorine is a halogen, not a heavy metal. It is a non-metallic element and is typically found in gaseous form.