A student constructs three identical simple circuits, each consisting of a 9.0 V battery, a switch, and either a copper wire segment, a crystal of solid sodium chloride, or a graphite rod as the only component completing the circuit between the battery terminals. The student closes each switch and observes whether a light-emitting diode (LED) connected in series illuminates.
Assume room temperature conditions and that the LED requires at least 0.15 A of current to emit visible light.
(a) Describe the type of bonding present in copper, solid sodium chloride, and graphite.
(b) For each circuit, explain whether the LED is expected to illuminate. In your explanation, identify the mobile charge carriers (if any) that allow or prevent conduction.
(c) Graphite is often described as a covalent network solid yet still conducts electricity. Explain how its particular structure accounts for this seemingly contradictory behavior.