Question

Solid state diamond is non conducting but graphite is conducting

Answer 1

Diamond is non-conducting but graphite is conducting.
This is because in diamond, one C-atom is bonded to 4 other carbon atoms in a tetrehedral manner and there are no free electrons to allow flow of electricity.
On the other hand, in graphite, one C-atom is bonded to 3 other C-atoms and there is one free electron for each C-atom. This electron is free to move and thus, allows the flow of electricity.
Hence, graphite can conduct electricity unlike diamond