Which of the following is not a good conductor of electricity?

Diamond

The correct answer is option 3. Diamond.

The substance that is not a good conductor of electricity is Diamond.

Diamond is not a good conductor of electricity because it consists of carbon atoms arranged in a tetrahedral lattice structure, where each carbon atom is covalently bonded to four other carbon atoms. This structure does not allow for the movement of free electrons, which are necessary for conducting electricity. Therefore, diamond is an insulator rather than a conductor of electricity.

Graphite, gold, and soil, on the other hand, are all known to be good conductors of electricity. Graphite, like diamond, is made of carbon atoms but has a different atomic arrangement that allows for the movement of electrons, making it a good conductor. Gold is an excellent conductor due to its high conductivity and malleability. Soil can conduct electricity due to the presence of moisture and dissolved ions, which allow for the flow of electric current.