Why are halogen poor conductor of both heat and electricity?

Answer 1

Halogens have 7 valence electrons (electrons in their last shell), this means that they require one more electron to become stable (Octet rule). Electricity and heat are conducted when atoms share electrons by bonding (ionic, covalent, and metallic). Metals are good conductors of heat and electricity because they have free moving electrons. Halogens tend to keep their electrons since they have a -1 charge. As one electron is gained for the halogen atoms (diatomic) become stable, it conducts electricity and heat. However, the conduction of heat and electricity is poor because it barely reacts (only one electron reacts). Compare this to any other element which has a higher charge as (+2, -2, +3, -3, etc.), then the other element will conduct heat and electricity better than a halogen. This is because more electrons are shared / reacted, more conduction of electricity and heat (Heat and electricity are sometimes the result of electron movement, or that electrons carry heat and electricity). Note: A special case is an alkali metal which also has one electron to donate, therefore it has a +1 charge. Alkali metals still conduct electricity and heat because they have free moving electrons (delocalized in a sea of electrons moving freely even without reacting). Basically, metals have their own structure where all the electrons move around freely conducting electricity (therefore its an amazing conductor).

Answer 2

Halogen atoms have high electronegativity, meaning they strongly attract electrons and do not readily give them up to conduct electricity. Additionally, halogen compounds tend to have stable structures that do not easily allow the flow of electric current. As for heat, halogens have low thermal conductivity due to their molecular structures, which restrict the transfer of heat energy.