Phosphorus (P) and sulfur (S) both are non-metals. Non-metals are good insulators i.e. they do not let electricity/current pass through them. The reason why non-metals are insulators is because they do not have free electrons in contrast to metals which have free electrons because of which they are good conductors of electricity.
Metals like Li (lithium), Ca (calcium), Ag (silver) and Au (gold) are conductors not insulators. Uranium (U) and thorium (Th) are radioactive but still they are metallic elements so they are not insulators.
