6 At STP, which element is a good conductor of electricity? (1) chlorine (3) silver

(2) iodine (4) sulfur

It would be Silver because it is metal.

For an object to conduct electricity it should have free or delocalised electrons that are free to pass the charge and hence take part in conducting electricity.

From the given choices

Chlorine is a halogen existing as a diatomic gas. Iodine too is a halogen and 2 Iodine atoms held together by covalent bond. Cl - Cl bonds and I-I bonds are covalent bonds. the outer electrons of Cl and I take part in covalent bonds therefore they are fixed and not free to move about. therefore no free electrons to conduct electricity.

Sulfur is a solid that too is held together by covalent bonds so it does not have free electrons to conduct electricity.

Silver is a metal and a general property of metals are their ability to conduct electricity.

metal structure are metal ions tightly packed together. when the metal atoms are tightly packed their valence electrons are removed and delocalised. Positively charged metal ions are embedded in a sea of delocalised electrons.

therefore there are delocalised electrons that can conduct electricity

answer is 3) silver